Federal Register / Vol. 72, No. 68 / Tuesday, April 10, 2007 / Notices 17849 

negligible impact on this species. In 

addition, NMFS has determined that 

bearded and spotted seals, if present 

within the vicinity of the project area 

could also be taken incidentally, by no 

more than Level B harassment and that 

such taking would have a negligible 

impact on such species or stocks. 

Although there is not a specfic number 

assessed for the taking of bearded and 

spotted seals due to their rare 

occurrence in the project area, NMFS 

believes that any take would be 

significantly lower than those of ringed 

seals. NMFS also finds that the action 

will not have an unmitigable adverse 

impact on the availability of such 

species or stocks for taking for 

subsistence uses. 

In addition, no take by Level A 

harassment (injury) or death is 

anticipated or authorized, and 

harassment takes should be at the 

lowest level practicable due to 

incorporation of the mitigation 

measures described in this document. 

Authorization 

NMFS has issued an IHA to SOI for 

the potential Level B harassment of 

small number of ringed seals, and 

potential Level B harassment of bearded 

and spotted seals incidental to 

conducting on-ice seismic R&D program 

in the U.S. Beaufort Sea, provided the 

previously mentioned mitigation, 

monitoring, and reporting requirements 

are incorporated. 

Dated: March 30, 2007. 

Angela Somma, 

Acting Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. E7–6653 Filed 4–9–07; 8:45 am] 

BILLING CODE 3510–22–S 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[I.D. 040307B] 

Small Takes of Marine Mammals 

Incidental to Specified Activities; LowEnergy Marine Seismic Survey in the 

Northeastern Indian Ocean, MayAugust 2007 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; proposed incidental 

take authorization; request for 

comments. 

SUMMARY: NMFS has received an 

application from Scripps Institute of 

Oceanography (SIO) for an Incidental 

Harassment Authorization (IHA) to take 

marine mammals incidental to 

conducting a low-energy marine seismic 

survey in the northeastern Indian Ocean 

during May-August 2007. Pursuant to 

the Marine Mammal Protection Act 

(MMPA), NMFS is requesting comments 

on its proposal to issue an IHA to SIO 

to incidentally take, by Level B 

harassment only, several species of 

marine mammals during the 

aforementioned activity. 

DATES: Comments and information must 

be received no later than May 10, 2007. 

ADDRESSES: Comments on the 

application should be addressed to 

Michael Payne, Chief, Permits, 

Conservation and Education Division, 

Office of Protected Resources, National 

Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD 

20910–3225. The mailbox address for 

providing email comments is 

PR1.040307B@noaa.gov. NMFS is not 

responsible for e-mail comments sent to 

addresses other than the one provided 

here. Comments sent via e-mail, 

including all attachments, must not 

exceed a 10–megabyte file size. 

A copy of the application containing 

a list of the references used in this 

document may be obtained by writing to 

the address specified above, telephoning 

the contact listed below (see FOR

FURTHER INFORMATION CONTACT), or 

visiting the internet at: http:// 

www.nmfs.noaa.gov/pr/permits/ 

incidental.htm#applications. 

Documents cited in this notice may be 

viewed, by appointment, during regular 

business hours, at the aforementioned 

address. 

FOR FURTHER INFORMATION CONTACT: Jolie 

Harrison, Office of Protected Resources, 

NMFS, (301) 713–2289, ext 166. 

SUPPLEMENTARY INFORMATION: 

Background 

Sections 101(a)(5)(A) and (D) of the 

MMPA (16 U.S.C. 1361 et seq.) direct 

the Secretary of Commerce to allow, 

upon request, the incidental, but not 

intentional, taking of marine mammals 

by U.S. citizens who engage in a 

specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

issued or, if the taking is limited to 

harassment, a notice of a proposed 

authorization is provided to the public 

for review. 

Authorization shall be granted if 

NMFS finds that the taking will have a 

negligible impact on the species or 

stock(s), will not have an unmitigable 

adverse impact on the availability of the 

species or stock(s) for subsistence uses 

(where relevant), and if the permissible 

methods of taking and requirements 

pertaining to the mitigation, monitoring 

and reporting of such takings are set 

forth. NMFS has defined ‘‘negligible 

impact’’ in 50 CFR 216.103 as ’’...an 

impact resulting from the specified 

activity that cannot be reasonably 

expected to, and is not reasonably likely 

to, adversely affect the species or stock 

through effects on annual rates of 

recruitment or survival.’’

Section 101(a)(5)(D) of the MMPA 

established an expedited process by 

which citizens of the United States can 

apply for an authorization to 

incidentally take small numbers of 

marine mammals by harassment. Except 

with respect to certain activities not 

pertinent here, the MMPA defines 

‘‘harassment’’ as: any act of pursuit, torment, or annoyance 

which (i) has the potential to injure a marine 

mammal or marine mammal stock in the wild 

[Level A harassment]; or (ii) has the potential 

to disturb a marine mammal or marine 

mammal stock in the wild by causing 

disruption of behavioral patterns, including, 

but not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

[Level B harassment]. 

Section 101(a)(5)(D) establishes a 45–

day time limit for NMFS review of an 

application followed by a 30–day public 

notice and comment period on any 

proposed authorizations for the 

incidental harassment of marine 

mammals. Within 45 days of the close 

of the comment period, NMFS must 

either approve or deny the 

authorization. 

Summary of Request 

On January 5, 2007, NMFS received 

an application from SIO for the taking, 

by Level B harassment only, of 32 

species of marine mammals incidental 

to conducting, with research funding 

from the National Science Foundation 

(NSF), a low-energy marine seismic 

survey in the northeastern Indian Ocean 

from May-August 2007. The purpose of 

the research program is to conduct a 

scientific rock-dredging, magnetic, 

bathymetric, and seismic survey 

program at nine sites on the Ninety East 

Ridge in the northeastern Indian Ocean. 

The results will be used to (1) determine 

the morphology, structure, and tectonics 

of ridge volcanoes to see whether they 

reflect centralized (plume) or 

distributed (crack) eruptions; (2) infer 

the magmatic evolution of the ridge, 

whether it fits the plume hypothesis, 

and its connection to existing hotspots; 

(3) examine the duration of volcanism at 

the various sites and along the ridge to 

see whether the age progression fits the 

simple plume model; and (4) survey 

broad characteristics of subseafloor in 


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order to refine the planning of the IODP 

drilling proposal. Included in the 

research planned for 2007 are scientific 

rock dredging at all nine sites, highresolution seismic methods to image the 

subsea floor at five of the sites, and the 

use of a magnetometer, gravimeter, 

multi-beam sonar, and sub-bottom 

profiler throughout the cruise. 

Description of the Activity 

The seismic surveys will involve one 

vessel, the R/V Roger Revelle (Roger 

Revelle), which is scheduled to depart 

from Fremantle, Australia, between May 

22 and June 19, 2007. The Roger Revelle 

will conduct the cruise in the Indian 

Ocean and arrive at Colombo, Sri Lanka, 

between July 16 and August 13, 2007. 

The exact dates of the activities may 

vary by a few days because of weather 

conditions, repositioning, streamer 

operations and adjustments, airgun 

deployment, or the need to repeat some 

lines if data quality is substandard. 

Additional seismic operations may be 

occasionally needed to investigate 

significant new findings as revealed by 

the other survey systems. The overall 

area within which the seismic surveys 

will occur is located between 

approximately 5° N. and 25° S., along 

approximately 90o E. (Figure 1 in the 

application), in the Indian Ocean. The 

surveys will be conducted entirely in 

International Waters. 

The Roger Revelle will deploy a pair 

of low-energy Generator-Injector (GI) 

airguns as an energy source (each with 

a discharge volume of 45 in3), plus a 

800 m-long (2625–ft long), 48–channel, 

towed hydrophone. The program will 

consist of approximately 2700 km (1678 

mi) of surveys, including turns. Water 

depths within the seismic survey areas 

are 1600–5100 m (1750–5577 yd). The 

GI guns will be operated on a small grid 

for approximately 49 hours at each of 5 

sites over a approximately 50–day 

period during May-August 2007, 

commencing between May 22 and June 

19. There will be additional seismic 

operations associated with equipment 

testing, start-up, and repeat coverage of 

any areas where initial data quality is 

sub-standard. 

In addition to the operations of the GI 

guns, a 3.5–kHz sub-bottom profiler , a 

Kongsberg-Simrad EM–120 multi-beam 

sonar, and a gravimeter will be used 

continuously throughout the cruise, and 

passive geophysical sensors will be 

deployed to conduct magnetic surveys 

at all times except during dredging. 

Vessel Specifications 

The Roger Revelle has a length of 83 

m (272 ft), a beam of 16 m (52 ft), and 

a maximum draft of 5.2 m. The ship is 

powered by two 3,000 hp Propulsion 

General Electric motors and an 1180–hp 

Azimuthing jet bow thruster. An 

operation speed of 11.1 km/h (6 knots) 

is used during seismic acquisition. 

When not towing seismic survey gear, 

the Roger Revelle cruises at 22.2–23.1 

km/h (12–12.5 knots) and has a 

maximum speed of 27.8 km/h (15 

knots). It has a normal operating range 

of approximately 27,780 km (17,262 mi). 

Acoustic Source Specifications 

Seismic Airguns 

The vessel Roger Revelle will tow a 

pair of GI airguns and an 800 m-long 

(2624–ft), 48–channel hydrophone 

streamer. Seismic pulses will be emitted 

at intervals of 6–10 seconds, which 

corresponds to a shot interval of 

approximatley 18.5–31 m (61–102 ft) (at 

a speed of 6 knots (11.1 km/h). The 

generator chamber of each GI gun, the 

one responsible for introducing the 

sound pulse into the ocean, is 45 in3

(total air discharge approximately 90 

in3). The larger (105 in3) injector 

chamber injects air into the previouslygenerated bubble to maintain its shape, 

and does not introduce more sound into 

the water. The two 45 in3 GI guns will 

be towed 8 m (26 ft) apart side by side, 

21 m (69 ft) behind the Roger Revelle, 

at a depth of 2 m (6.6 ft). The dominant 

frequency components are 0–188 Hz. 

The sound pressure field of that GI 

gun variation has not been modeled, but 

that for two 45 in3 Nucleus G guns 

(which actually have more energy than 

GI guns of the same size) has been 

modeled by the Lamont-Doherty Earth 

Observatory (L-DEO) in relation to 

distance and direction from the airguns. 

This source, which is directed 

downward, was found to have an output 

(0–peak) of 230.6 dB re 1 μPa m. The 

nominal downward-directed source 

levels indicated above do not represent 

actual sound levels that can be 

measured at any location in the water. 

Rather, they represent the level that 

would be found 1 m from a hypothetical 

point source emitting the same total 

amount of sound as is emitted by the 

combined GI guns. The actual received 

level at any location in the water near 

the GI guns will not exceed the source 

level of the strongest individual source. 

In this case, that will be about 224.6 dB 

re 1 μPa-m peak, or 229.8 dB re 1 μPam peak-to-peak. Actual levels 

experienced by any organism more than 

1 m from either GI gun will be 

significantly lower. 

A further consideration is that the rms 

(root mean square) received levels that 

are used as impact criteria for marine 

mammals are not directly comparable to 

the peak or peak to peak values 

normally used to characterize source 

levels of airgun arrays. The 

measurement units used to describe 

airgun sources, peak or peak-to-peak 

decibels, are always higher than the 

‘‘root mean square’’ (rms) decibels 

referred to in biological literature. A 

measured received level of 160 dB rms 

in the far field would typically 

correspond to a peak measurement of 

approximately 170 to 172 dB, and to a 

peak-to-peak measurement of 

approximately 176 to 178 dB, as 

measured for the same pulse received at 

the same location (Greene 1997; 

McCauley et al., 1998, 2000). The 

precise difference between rms and 

peak or peak-to-peak values depends on 

the frequency content and duration of 

the pulse, among other factors. 

However, the rms level is always lower 

than the peak or peak-to-peak level for 

an airgun-type source. 

Bathymetric Sonar 

The Roger Revelle will utilize the 

Kongsberg-Simrad EM120 multi-beam 

sonar, which operates at 11.25–12.6 kHz 

and is mounted in the hull. It operates 

in several modes, depending on water 

depth. In the proposed survey, it will be 

used in deep (>800–m (2625 ft)) water, 

and will operate in ‘‘Deep’’ mode. The 

beam width is 1° or 2° fore-aft and a 

total of 150° athwartship. Estimated 

maximum source levels are 239 and 233 

dB at 1° and 2° beam widths, 

respectively. Each ‘‘ping’’ consists of 

nine successive fan-shaped 

transmissions, each ensonifying a sector 

that extends 1° or 2° fore-aft. In the 

‘‘Deep’’ mode, the total duration of the 

transmission into each sector is 15 ms. 

The nine successive transmissions span 

an overall cross-track angular extent of 

about 150 degrees, with 16 ms gaps 

between the pulses for successive 

sectors. A receiver in the overlap area 

between two sectors would receive two 

15–ms pulses separated by a 16–ms gap. 

The ‘‘ping’’ interval varies with water 

depth, from approximately 5 s at 1000 

m (3280 ft) to 20 s at 4000 m (13120 ft). 

Sub-bottom Profiler 

The Roger Revelle will utilize the 

Knudsen Engineering Model 320BR subbottom profiler, which is a dualfrequency transceiver designed to 

operate at 3.5 and/or 12 kHz. It is used 

in conjunction with the multi-beam 

sonar to provide data about the 

sedimentary features that occur below 

the sea floor. The energy from the subbottom profiler is directed downward 

(in an 80–degree cone) via a 3.5–kHz 

transducer array mounted in the hull. 

The maximum power output of the 


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320BR is 10 kilowatts for the 3.5–kHz 

section and 2 kilowatts for the 12–kHz 

section. (The 12–kHz section is seldom 

used in survey mode on Roger Revelle 

because of overlap with the operating 

frequency of the Kongsberg Simrad EM–

120 multi-beam sonar.) 

The pulse length for the 3.5 kHz 

section of the 320BR is 0.8–24 ms, 

controlled by the system operator in 

regards to water depth and reflectivity 

of the bottom sediments, and will 

usually be 12 or 24 ms in this survey. 

The system produces one sound pulse 

and then waits for its return before 

transmitting again. Thus, the pulse 

interval is directly dependent upon 

water depth, and in this survey is 4.5–

8 sec. Using the Sonar Equations and 

assuming 100 percent efficiency in the 

system (impractical in real world 

applications), the source level for the 

320BR is calculated to be 211 dB re 1 

μPa-m. In practice, the system is rarely 

operated above 80 percent power level. 

Safety Radii 

NMFS has determined that for 

acoustic effects, using acoustic 

thresholds in combination with 

corresponding safety radii is the most 

effective way to consistently apply 

measures to avoid or minimize the 

impacts of an action, and to 

quantitatively estimate the effects of an 

action. Thresholds are used in two 

ways: (1) to establish a mitigation shutdown or power down zone, i.e., if an 

animal enters an area calculated to be 

ensonified above the level of an 

established threshold, a sound source is 

powered down or shut down; and (2) to 

calculate take, in that a model may be 

used to calculate the area around the 

sound source that will be ensonified to 

that level or above, then, based on the 

estimated density of animals and the 

distance that the sound source moves, 

NMFS can estimate the number of 

marine mammals that may be ‘‘taken’’. 

NMFS believes that to avoid permanent 

physiological damage (Level A 

Harassment), cetaceans and pinnipeds 

should not be exposed to pulsed 

underwater noise at received levels 

exceeding, respectively, 180 and 190 dB 

re 1 μPa (rms). NMFS also assumes that 

cetaceans or pinnipeds exposed to 

levels exceeding 160 dB re 1 μPa (rms) 

may experience Level B Harassment. 

Received sound levels have been 

modeled by L-DEO for a number of 

airgun configurations, including two 

45–in3 Nucleus G-guns, in relation to 

distance and direction from the airguns. 

The model does not allow for bottom 

interactions, and is most directly 

applicable to deep water. Based on the 

modeling, estimates of the maximum 

distances from the GI guns where sound 

levels of 190, 180, and 160 dB re 1 μPa 

(rms) are predicted to be received in 

deep (≤1000–m (3280–ft)) water are 10, 

40, and 400 m (33, 131, and 1312 ft), 

respectively. Because the model results 

are for G guns, which have more energy 

than GI guns of the same size, those 

distances are overestimates of the 

distances for the 45–in3 GI guns. 

Empirical data concerning the 180- 

and 160- dB distances have been 

acquired based on measurements during 

the acoustic verification study 

conducted by L-DEO in the northern 

Gulf of Mexico from 27 May to 3 June 

2003 (Tolstoy et al., 2004). Although the 

results are limited, the data showed that 

radii around the airguns where the 

received level would be 180 dB re 1 μPa 

(rms) vary with water depth. Similar 

depth-related variation is likely in the 

190–dB distances applicable to 

pinnipeds. Correction factors were 

developed for water depths 100–1000 m 

(328–3280 ft) and <100 m (328 ft). The 

proposed survey will occur in depths 

1600–5100 m (5249–16732 ft), so the 

correction factors are not relevant here. 

The empirical data indicate that, for 

deep water (>1000 m (3280 ft)), the LDEO model tends to overestimate the 

received sound levels at a given 

distance (Tolstoy et al., 2004). However, 

to be precautionary pending acquisition 

of additional empirical data, it is 

proposed that safety radii during airgun 

operations in deep water will be the 

values predicted by L-DEO’s model 

(above). Therefore, the assumed 180- 

and 190–dB radii are 40 m and 10 m 

(131 and 33 ft), respectively. 

Airguns will be shut down 

immediately when cetaceans or 

pinnipeds are detected within or about 

to enter the appropriate 180–dB (rms) or 

190–dB (rms) radius, respectively. 

Description of Marine Mammals in the 

Activity Area 

Thirty-two species of cetacean, 

including 25 odontocete (dolphins and 

small and large toothed whales) species 

and seven mysticete (baleen whales) 

species, are thought to occur in the 

proposed seismic survey areas along the 

Ninety East Ridge in the northeastern 

Indian Ocean (Table 1). Several are 

listed under the U.S. Endangered 

Species Act (ESA) as Endangered: the 

sperm whale, humpback whale, blue 

whale, fin whale, and sei whale. 

Although there have been several 

surveys of marine mammals in the 

Indian Ocean (e.g., Keller et al., 1982; 

Leatherwood et al., 1984; Eyre 1995; 

Baldwin et al., 1998; de Boer 2000; de 

Boer et al., 2003), data on the 

occurrence, distribution, and abundance 

of odontocetes and mysticetes in the 

northeastern Indian Ocean, 

encompassing the proposed seismic 

survey area along the Ninety East Ridge, 

are limited or lacking. Commercial 

whaling severely depleted all the large 

whale populations in this region, and 

subsequently, in 1979, the International 

Whaling Commission declared the 

Indian Ocean north of 55° S. latitude a 

whale sanctuary. The majority of recent 

detailed information on whales within 

the Indian Ocean Sanctuary (IOS) comes 

from 

(1) A United Nations Environment 

Programme (UNEP) Report summarizing 

cetacean research in the western IOS 

(Leatherwood and Donovan 1991); 

(2) A compilation of sightings for the 

entire IOS produced by the Whale and 

Dolphin Conservation Society (de Boer 

et al., 2003); and 

(3) A review of marine mammals 

records in India (Sathasivam 2004); and 

(4) A series of research cruises within 

the IOS (Keller et al., 1982; 

Leatherwood et al., 1984; Corbett 1994; 

Eyre 1995; Ballance and Pitman 1998; 

de Boer 2000). 

Because the proposed survey area 

spans such a wide range of latitudes 

(approximately 5° N.-25° S.), tropical 

and temperate species are found there. 

The survey area is all in deep-water 

habitat but is close to oceanic island 

habitats (i.e., Andaman, Nicobar, and 

Cocos (Keeling) Islands), so both coastal 

and oceanic species might be 

encountered, although species that stay 

in very shallow water (e.g., Indian 

hump-backed dolphin, Irrawaddy 

dolphin, and finless porpoise) would 

not. Abundance and density estimates 

of cetaceans found in areas other than 

the northeastern and central Indian 

Ocean are provided for reference only, 

and are not necessarily the same as 

those in the survey area. Table 1 also 

shows the estimated abundance of the 

marine mammals likely to be 

encountered during the Roger Revelle’s 

cruise. Additional information regarding 

the distribution of these species and 

how the estimated densities were 

calculated may be found in SIO’s 

application. 


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Species Habitat Occurrence Rqstd Take 

Mysticetes 

Humpback whale (Megaptera 

novaeangliae)* 

Mainly nearshore waters and banks Common 5(0)** 

Minke whale (Balaenoptera acutorostrata) Pelagic and coastal Uncommon 5 

Antarctic minke whale (Balaenoptera 

bonaerensis) 

Coastal and oceanic Uncommon 5 

Bryde’s whale (Balaenoptera edeni) Pelagic and coastal Very common 5 

Sei whale (Balaenoptera borealis) * Primarily offshore, pelagic Uncommon 5(0)** 

Fin whale (Balaenoptera physalus)* Continental slope, mostly pelagic Common 5(0)** 

Blue whale (Balaenoptera musculus)* Pelagic and coastal Very common 5(1)** 

Odontocetes 

Sperm whale (Physeter macrocephalus)* Usually pelagic and deep seas Common 5(1)** 

Pygmy sperm whale (Kogia breviceps) Deep waters off the shelf Common 5 

Dwarf sperm whale (Kogia sima) Deep waters off the shelf Common 5 

Cuvier’s beaked whale (Ziphius cavirostris) Pelagic Common 5 

Shepherd’s beaked whale (Tasmacetus 

shepherdi)) 

Pelagic Rare 5 

Longman’s beaked whale (Indopacetus 

pacificus) 

Pelagic Common? 1 

Southern bottlenose whale (Hyperoodon 

planifrons) 

Pelagic Uncommon 5 

True’s beaked whale (Mesoplodon mirus) Pelagic Rare 5 

Gray’s beaked whale (Mesoplodon grayi) Pelagic Uncommon 5 

Ginkgo-toothed whale (Mesoplodon 

ginkgodens) 

Pelagic Common 5 

Blainville’s beaked whale (Mesoplodon 

densirostris) 

Pelagic Very common 5 

Rough-toothed dolphin (Steno bredanensis) Deep water Uncommon 69 

Bottlenose dolphin (Tursiops truncatus) Coastal and oceanic, shelf break Common 129 

Pantropical spotted dolphin (Stenella 

attenuata) 

Coastal and pelagic Uncommon 65 

Spinner dolphin (Stenella longirostris) Coastal and pelagic Abundant 215 

Striped dolphin (Stenella coeruleoalba) Off continental shelf Common 86 

Fraser’s dolphin (Lagenodelphis hosei) Waters >1000 m Rare 22 

Common dolphin (Delphinus delphis) Shelf and pelagic, seamounts Very common 151 

Risso’s dolphin (Grampus griseus) Waters >1000 m, seamounts Very common 151 

Melon-headed whale (Peponocephala 

electra) 

Oceanic Very common 50 

Pygmy killer whale (Feresa attenuata) Deep, pantropical waters Common 25 

False killer whale (Pseudorca crassidens) Pelagic Common 15 

Killer whale (Orcinus orca) Widely distributed Common 5 

Long-finned pilot whale (Globicephala 

melas) 

Mostly pelagic Rare 30 


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Species Habitat Occurrence Rqstd Take 

Short-finned pilot whale (Globicephala 

macrorhynchus) 

Mostly pelagic, high-relief topography Very common 15 

Table 1. Species expected to be encountered (and potentially harassed) during SIO’s Indian Ocean cruise 

*Species are listed as endangered under the Endangered Species Act 

**Parenthetical numbers represent numbers of takes NMFS proposes to authorize (we may not authorize take ofspecies, or take of numbers of 

species, that we are not exempted pursuant to our internal ESA consultation) 

Potential Effects on Marine Mammals 

Potential Effects of Airguns 

The effects of sounds from airguns 

might include one or more of the 

following: tolerance, masking of natural 

sounds, behavioral disturbance, and 

temporary or permanent hearing 

impairment (Richardson et al., 1995). 

Given the small size of the GI guns 

planned for the present project, effects 

are anticipated to be considerably less 

than would be the case with a large 

array of airguns. It is very unlikely that 

there would be any cases of temporary 

or, especially, permanent hearing 

impairment. Also, behavioral 

disturbance is expected to be limited to 

relatively short distances. 

Tolerance 

Numerous studies have shown that 

pulsed sounds from airguns are often 

readily detectable in the water at 

distances of many kilometers. For a 

summary of the characteristics of airgun 

pulses, see Appendix A of SIO’s 

application. However, it should be 

noted that most of the measurements of 

airgun sounds that have been reported 

concerned sounds from larger arrays of 

airguns, whose sounds would be 

detectable considerably farther away 

than the GI guns planned for use in the 

present project. 

Numerous studies have shown that 

marine mammals at distances more than 

a few kilometers from operating seismic 

vessels often show no apparent 

response-see Appendix A (e) of SIO’s 

application. That is often true even in 

cases when the pulsed sounds must be 

readily audible to the animals based on 

measured received levels and the 

hearing sensitivity of that mammal 

group. Although various baleen whales, 

toothed whales, and (less frequently) 

pinnipeds have been shown to react 

behaviorally to airgun pulses under 

some conditions, at other times 

mammals of all three types have shown 

no overt reactions. In general, pinnipeds 

and small odontocetes seem to be more 

tolerant of exposure to airgun pulses 

than are baleen whales. Given the 

relatively small and low-energy airgun 

source planned for use in this project, 

mammals (and sea turtles) are expected 

to tolerate being closer to this source 

than might be the case for a larger 

airgun source typical of most seismic 

surveys. 

Masking 

Masking effects of pulsed sounds 

(even from large arrays of airguns) on 

marine mammal calls and other natural 

sounds are expected to be limited, 

although there are very few specific data 

on this. Some whales are known to 

continue calling in the presence of 

seismic pulses. Their calls can be heard 

between the seismic pulses (e.g., 

Richardson et al., 1986; McDonald et al., 

1995; Greene et al., 1999; Nieukirk et 

al., 2004). Although there has been one 

report that sperm whales cease calling 

when exposed to pulses from a very 

distant seismic ship (Bowles et al., 

1994), a recent study reports that sperm 

whales off northern Norway continued 

calling in the presence of seismic pulses 

(Madsen et al., 2002c). That has also 

been shown during recent work in the 

Gulf of Mexico (Tyack et al., 2003). 

Given the small source planned for use 

here, there is even less potential for 

masking of baleen or sperm whale calls 

during the present study than in most 

seismic surveys. Masking effects of 

seismic pulses are expected to be 

negligible in the case of the smaller 

odontocete cetaceans, given the 

intermittent nature of seismic pulses 

and the relatively low source level of 

the airguns to be used here. Also, the 

sounds important to small odontocetes 

are predominantly at much higher 

frequencies than are airgun sounds. 

Masking effects, in general, are 

discussed further in Appendix A (d) of 

SIO’s application. 

Disturbance Reactions 

Disturbance includes a variety of 

effects, including subtle changes in 

behavior, more conspicuous changes in 

activities, and displacement. 

Disturbance is one of the main concerns 

in this project. Reactions to sound, if 

any, depend on species, state of 

maturity, experience, current activity, 

reproductive state, time of day, and 

many other factors. If a marine mammal 

responds to an underwater sound by 

changing its behavior or moving a small 

distance, the response may or may not 

rise to the level of harassment, let alone 

affect the stock or the species as a 

whole. Alternatively, if a sound source 

displaces marine mammals from an 

important feeding or breeding area, 

effects on the stock or species could 

potentially be more than negligible. 

Given the many uncertainties in 

predicting the quantity and types of 

impacts of noise on marine mammals, it 

is common practice to estimate how 

many mammals are likely to be present 

within a particular distance of industrial 

activities, or exposed to a particular 

level of industrial sound. This practice 

potentially overestimates the numbers 

of marine mammals that are affected in 

some biologically important manner. 

The sound criteria used to estimate 

how many marine mammals might be 

disturbed to some biologicallyimportant degree by a seismic program 

are based on behavioral observations 

during studies of several species. 

However, information is lacking for 

many species. Detailed studies have 

been done on humpback, gray, and 

bowhead whales, and on ringed seals. 

Less detailed data are available for some 

other species of baleen whales, sperm 

whales, and small toothed whales. Most 

of those studies have focused on the 

impacts resulting from the use of much 

larger airgun sources than those planned 

for use in the present project. Thus, 

effects are expected to be limited to 

considerably smaller distances and 

shorter periods of exposure in the 

present project than in most of the 

previous work concerning marine 

mammal reactions to airguns. 

Baleen Whales – Baleen whales 

generally tend to avoid operating 

airguns, but avoidance radii are quite 

variable. Whales are often reported to 

show no overt reactions to pulses from 

large arrays of airguns at distances 

beyond a few kilometers, even though 

the airgun pulses remain well above 

ambient noise levels out to much longer 

distances. However, as reviewed in 

Appendix A (e) of SIO’s application, 

baleen whales exposed to strong noise 

pulses from airguns often react by 

deviating from their normal migration 

route and/or interrupting their feeding 

activities and moving away from the 

sound source. In the case of the 

migrating gray and bowhead whales, the 

observed changes in behavior appeared 


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to be of little or no biological 

consequence to the animals. They 

simply avoided the sound source by 

displacing their migration route to 

varying degrees, but within the natural 

boundaries of the migration corridors. 

Studies of gray, bowhead, and 

humpback whales have determined that 

received levels of pulses in the 160–170 

dB re 1 μPa rms range seem to cause 

obvious avoidance behavior in a 

substantial fraction of the animals 

exposed. In many areas, seismic pulses 

from large arrays of airguns diminish to 

those levels at distances ranging from 

4.5–14.5 km (2.8–9 mi) from the source. 

A substantial proportion of the baleen 

whales within those distances may 

show avoidance or other strong 

disturbance reactions to the airgun 

array. Subtle behavioral changes 

sometimes become evident at somewhat 

lower received levels, and recent 

studies, reviewed in Appendix A (e) of 

SIO’s application, have shown that 

some species of baleen whales, notably 

bowheads and humpbacks, at times 

show strong avoidance at received 

levels lower than 160–170 dB re 1 μPa 

rms. Reaction distances would be 

considerably smaller during the present 

project, in which the 160–dB radius is 

predicted to be approximately 0.40 km 

(0.9 mi), as compared with several 

kilometers when a large array of airguns 

is operating. 

Humpback whales summering in 

southeast Alaska did not exhibit 

persistent avoidance when exposed to 

seismic pulses from a 1.64–L (100 in3) 

airgun (Malme et al., 1985). Some 

humpbacks seemed ‘‘startled’’ at 

received levels of 150–169 dB re 1 μPa 

on an approximate rms basis. Malme et 

al. (1985) concluded that there was no 

clear evidence of avoidance, despite the 

possibility of subtle effects, at received 

levels up to 172 re 1 μPa (approximately 

rms). More detailed information on 

responses of humpback whales to 

seismic pulses during studies in 

Australia can be found in Appendix A 

(a) of SIO’s application. 

Malme et al. (1986, 1988) studied the 

responses of feeding eastern gray whales 

to pulses from a single 100 in3 airgun 

off St. Lawrence Island in the northern 

Bering Sea. They estimated, based on 

small sample sizes, that 50 percent of 

feeding gray whales ceased feeding at an 

average received pressure level of 173 

dB re 1 μPa on an (approximate) rms 

basis, and that 10 percent of feeding 

whales interrupted feeding at received 

levels of 163 dB. Those findings were 

generally consistent with the results of 

experiments conducted on larger 

numbers of gray whales that were 

migrating along the California coast. 

Data on short-term reactions (or lack 

of reactions) of cetaceans to impulsive 

noises do not necessarily provide 

information about long-term effects. It is 

not known whether impulsive noises 

affect reproductive rate or distribution 

and habitat use in subsequent days or 

years. However, gray whales continued 

to migrate annually along the west coast 

of North America despite intermittent 

seismic exploration and much ship 

traffic in that area for decades 

(Appendix A in Malme et al., 1984). 

Bowhead whales continued to travel to 

the eastern Beaufort Sea each summer 

despite seismic exploration in their 

summer and autumn range for many 

years (Richardson et al., 1987). In any 

event, the brief exposures to sound 

pulses from the present small airgun 

source are highly unlikely to result in 

prolonged effects. 

Toothed Whales – Little systematic 

information is available about reactions 

of toothed whales to noise pulses. Few 

studies similar to the more extensive 

baleen whale/seismic pulse work 

summarized above have been reported 

for toothed whales. However, systematic 

work on sperm whales is underway 

(Tyack et al., 2003). 

Seismic operators sometimes see 

dolphins and other small toothed 

whales near operating airgun arrays, but 

in general there seems to be a tendency 

for most delphinids to show some 

limited avoidance of seismic vessels 

operating large airgun systems. 

However, some dolphins seem to be 

attracted to the seismic vessel and 

floats, and some ride the bow wave of 

the seismic vessel even when large 

arrays of airguns are firing. Nonetheless, 

there have been indications that small 

toothed whales sometimes tend to head 

away, or to maintain a somewhat greater 

distance from the vessel, when a large 

array of airguns is operating than when 

it is silent (e.g., Goold, 1996; 

Calambokidis and Osmek, 1998; Stone, 

2003). Similarly, captive bottlenose 

dolphins and beluga whales exhibit 

changes in behavior when exposed to 

strong pulsed sounds similar in 

duration to those typically used in 

seismic surveys (Finneran et al., 2000, 

2002). However, the animals tolerated 

high received levels of sound (pk-pk 

level >200 dB re 1 μPa) before exhibiting 

aversive behaviors. With the presentlyplanned small airgun system, such 

levels would only be found within a few 

meters of the airguns. 

There are no specific data on the 

behavioral reactions of beaked whales to 

seismic surveys. A few beaked whale 

sightings have been reported from 

seismic vessels (Stone, 2003), however, 

based on limited observations most 

beaked whales tend to avoid 

approaching vessels of other types (e.g., 

Kasuya, 1986; Wursig et al., 1998). 

Several beaked whale strandings have 

been associated with naval midfrequency sonar exercises, however, the 

sounds produced by seismic airguns are 

quite different from tactical sonar (see 

Appendix A (g) of SIO’s application). 

The strandings mentioned above are 

apparently at least in part a disturbance 

response, although auditory or other 

injuries may also be a factor. Whether 

beaked whales would ever react 

similarly to seismic surveys is unknown 

(see ‘‘Strandings and Mortality’’, below). 

Sperm whales have been reported to 

show avoidance reactions to standard 

vessels not emitting airgun sounds, and 

it is to be expected that they would tend 

to avoid an operating seismic survey 

vessel. There were some limited early 

observations suggesting that sperm 

whales in the Southern Ocean and Gulf 

of Mexico might be fairly sensitive to 

airgun sounds from distant seismic 

surveys. However, more extensive data 

from recent studies in the North 

Atlantic suggest that sperm whales in 

those areas show little evidence of 

avoidance or behavioral disruption in 

the presence of operating seismic 

vessels (McCall Howard, 1999; Madsen 

et al., 2002c; Stone, 2003). 

Odontocete reactions to large arrays of 

airguns are variable and, at least for 

small odontocetes, seem to be confined 

to a smaller radius than has been 

observed for mysticetes. Thus, 

behavioral reactions of odontocetes to 

the small airgun source to be used here 

are expected to be very localized, 

probably to distances <0.40 km (.25 mi). 

Pinnipeds – Pinnipeds are not likely 

to show a strong avoidance reaction to 

the small airgun source that will be 

used. Visual monitoring from seismic 

vessels, usually employing larger 

sources, has shown only slight (if any) 

avoidance of airguns by pinnipeds, and 

only slight (if any) changes in behaviorsee Appendix A (e) of SIO’s application. 

Those studies show that pinnipeds 

frequently do not avoid the area within 

a few hundred meters of operating 

airgun arrays, even for arrays much 

larger than the one to be used here (e.g., 

Harris et al., 2001). However, initial 

telemetry work suggests that avoidance 

and other behavioral reactions to small 

airgun sources may be stronger than 

evident to date from visual studies of 

pinniped reactions to airguns 

(Thompson et al., 1998). Even if 

reactions of the species occurring in the 

present study area are as strong as those 

evident in the telemetry study, reactions 

are expected to be confined to relatively 


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small distances and durations, with no 

long-term effects on pinnipeds. 

Additional details on the behavioral 

reactions (or the lack thereof) by all 

types of marine mammals to seismic 

vessels can be found in Appendix A (e) 

of SIO’s application. 

Hearing Impairment and Other Physical 

Effects 

Temporary or permanent hearing 

impairment is a possibility when marine 

mammals are exposed to very strong 

sounds, but there has been no specific 

documentation of this for marine 

mammals exposed to sequences of 

airgun pulses. Current NMFS policy 

regarding exposure of marine mammals 

to high-level sounds is that cetaceans 

and pinnipeds should not be exposed to 

impulsive sounds of 180 and 190 dB re 

1 μPa (rms), respectively. Those criteria 

have been used in defining the safety 

(shut-down) radii planned for the 

proposed seismic survey. The 

precautionary nature of these criteria is 

discussed in Appendix A (f) of SIO’s 

application, including the fact that the 

minimum sound level necessary to 

cause permanent hearing impairment is 

higher, by a variable and generally 

unknown amount, than the level that 

induces barely-detectable temporary 

threshold shift (TTS) (which NMFS’

criteria are based on) and the level 

associated with the onset of TTS is often 

considered to be a level below which 

there is no danger of permanent damage. 

NMFS is presently developing new 

noise exposure criteria for marine 

mammals that take account of the nowavailable data on TTS in marine (and 

terrestrial) mammals. 

Because of the small size of the airgun 

source in this project (two 45–in3 GI 

guns), along with the planned 

monitoring and mitigation measures, 

there is little likelihood that any marine 

mammals will be exposed to sounds 

sufficiently strong to cause hearing 

impairment. Several aspects of the 

planned monitoring and mitigation 

measures for this project are designed to 

detect marine mammals occurring near 

the two GI airguns (and multi-beam 

bathymetric sonar), and to avoid 

exposing them to sound pulses that 

might, at least in theory, cause hearing 

impairment. In addition, many 

cetaceans are likely to show some 

avoidance of the area with high received 

levels of airgun sound (see above). In 

those cases, the avoidance responses of 

the animals themselves will reduce or 

(most likely) avoid any possibility of 

hearing impairment. 

Non-auditory physical effects may 

also occur in marine mammals exposed 

to strong underwater pulsed sound. 

Possible types of non-auditory 

physiological effects or injuries that 

theoretically might occur in mammals 

close to a strong sound source include 

stress, neurological effects, bubble 

formation, resonance effects, and other 

types of organ or tissue damage. It is 

possible that some marine mammal 

species (i.e., beaked whales) may be 

especially susceptible to injury and/or 

stranding when exposed to strong 

pulsed sounds. However, as discussed 

below, there is no definitive evidence 

that any of these effects occur even for 

marine mammals in close proximity to 

large arrays of airguns. It is especially 

unlikely that any effects of these types 

would occur during the present project 

given the small size of the source, the 

brief duration of exposure of any given 

mammal, and the planned monitoring 

and mitigation measures (see below). 

The following subsections discuss in 

somewhat more detail the possibilities 

of TTS, permanent threshold shift 

(PTS), and non-auditory physical 

effects. 

Temporary Threshold Shift (TTS) –

TTS is the mildest form of hearing 

impairment that can occur during 

exposure to a strong sound (Kryter, 

1985). While experiencing TTS, the 

hearing threshold rises and a sound 

must be stronger in order to be heard. 

TTS can last from minutes or hours to 

(in cases of strong TTS) days. For sound 

exposures at or somewhat above the 

TTS threshold, hearing sensitivity 

recovers rapidly after exposure to the 

noise ends. Only a few data on sound 

levels and durations necessary to elicit 

mild TTS have been obtained for marine 

mammals, and none of the published 

data concern TTS elicited by exposure 

to multiple pulses of sound. 

For toothed whales exposed to single 

short pulses, the TTS threshold appears 

to be, to a first approximation, a 

function of the energy content of the 

pulse (Finneran et al., 2002). Given the 

available data, the received level of a 

single seismic pulse might need to be 

approximately 210 dB re 1 μPa rms 

(approximately 221–226 dB pk-pk) in 

order to produce brief, mild TTS. 

Exposure to several seismic pulses at 

received levels near 200–205 dB (rms) 

might result in slight TTS in a small 

odontocete, assuming the TTS threshold 

is (to a first approximation) a function 

of the total received pulse energy. 

Seismic pulses with received levels of 

200–205 dB or more are usually 

restricted to a radius of no more than 

100 m (328 ft) around a seismic vessel 

operating a large array of airguns. Such 

levels would be limited to distances 

within a few meters of the small GI-gun 

source to be used in this project. 

For baleen whales, there are no data, 

direct or indirect, on levels or properties 

of sound that are required to induce 

TTS. However, no cases of TTS are 

expected given the small size of the 

source, and, as mentioned previously, 

there is a strong likelihood that baleen 

whales would avoid the approaching GI 

gun (or vessel), with the sound source 

operating, before being exposed to levels 

high enough for there to be any 

possibility of TTS. 

In pinnipeds, TTS thresholds 

associated with exposure to brief pulses 

(single or multiple) of underwater sound 

have not been measured. Initial 

evidence from prolonged exposures 

suggested that some pinnipeds may 

incur TTS at somewhat lower received 

levels than do small odontocetes 

exposed for similar durations (Kastak et 

al., 1999; Ketten et al., 2001; cf. Au et 

al., 2000). However, more recent 

indications are that TTS onset in the 

most sensitive pinniped species studied 

(harbor seal) may occur at a similar 

sound exposure level as in odontocetes 

(Kastak et al., 2004). 

A marine mammal within a radius of 

100 m (328 ft) around a typical large 

array of operating airguns might be 

exposed to a few seismic pulses with 

levels of 205 dB, and possibly more 

pulses if the mammal moved with the 

seismic vessel. (As noted above, most 

cetacean species tend to avoid operating 

airguns, although not all individuals do 

so.) In addition, ramping up airgun 

arrays, which is standard operational 

protocol for large airgun arrays, 

provides an opportunity for cetaceans to 

move away from the seismic source and 

to avoid being exposed to the full 

acoustic output of the airgun array. 

However, several of the considerations 

that are relevant in assessing the impact 

of typical seismic surveys with arrays of 

airguns are not directly applicable here: 

(1) The planned GI gun source is 

much smaller, with correspondingly 

smaller radii within which received 

sound levels could exceed any 

particular level of concern. 

(2) With a large airgun array, it is 

unlikely that cetaceans would be 

exposed to airgun pulses at a 

sufficiently high level for a sufficiently 

long period to cause more than mild 

TTS, given the relative movement of the 

vessel and the marine mammal. In this 

project, the gun source is much smaller, 

so the radius of influence and duration 

of exposure to strong pulses is much 

smaller, especially in deep and 

intermediate-depth water. 

(3) With a large array of airguns, TTS 

would be most likely in any odontocetes 

that bow-ride or otherwise linger near 

the airguns. In the present project, the 


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anticipated 180–dB distance in deep 

water is 40 m (131 ft), and the waterline 

at the bow of the Roger Revelle will be 

approximately 97 m (318 ft) ahead of the 

GI gun. 

To avoid injury, NMFS has 

determined that cetaceans and 

pinnipeds should not be exposed to 

pulsed underwater noise at received 

levels exceeding, respectively, 180 and 

190 dB re 1 μPa (rms). The predicted 

180- and 190–dB distances for the GI 

guns operated by SIO are 40 m (131 ft) 

and 10 m (33 ft), respectively, in water 

depths >1000 m (3280 ft). [Those 

distances actually apply to operations 

with two 45–in3 G guns, and smaller 

distances would be expected for the two 

45–in3 GI guns to be used here.] These 

sound levels are the received levels 

above which, in the view of a panel of 

bioacoustics specialists convened by 

NMFS, one cannot be certain that there 

will be no injurious effects, auditory or 

otherwise, to marine mammals. More 

recent TTS data imply that, at least for 

dolphins, TTS is unlikely to occur 

unless the dolphins are exposed to 

airgun pulses notably stronger than 180 

dB re 1 μPa rms. However NMFS 

utilizes a precautionary approach of 

requiring shut down at received levels 

above which we cannot be certain there 

will be no injurious effects to the most 

sensitive species. 

Permanent Threshold Shift (PTS) –

When PTS occurs, there is physical 

damage to the sound receptors in the 

ear. In some cases, there can be total or 

partial deafness, while in other cases, 

the animal has an impaired ability to 

hear sounds in specific frequency 

ranges. There is no specific evidence 

that exposure to pulses of airgun sound 

can cause PTS in any marine mammal, 

even with large arrays of airguns. 

However, given the possibility that 

mammals close to an airgun array might 

incur TTS, there has been further 

speculation about the possibility that 

some individuals occurring very close to 

airguns might incur PTS. Single or 

occasional occurrences of mild TTS are 

not indicative of permanent auditory 

damage in terrestrial mammals. 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals, but are assumed to be 

similar to those in humans and other 

terrestrial mammals. PTS might occur at 

a received sound level 20 dB or more 

above that inducing mild TTS if the 

animal were exposed to the strong 

sound for an extended period, or to a 

strong sound with rather rapid rise timesee Appendix A (f) of SIO’s application. 

It is highly unlikely that marine 

mammals could receive sounds strong 

enough to cause permanent hearing 

impairment during a project employing 

two 45–in3 GI guns. In the present 

project, marine mammals are unlikely to 

be exposed to received levels of seismic 

pulses strong enough to cause TTS, as 

they would probably need to be within 

a few meters of the airguns for that to 

occur. Given the higher level of sound 

necessary to cause PTS, it is even less 

likely that PTS could occur. In fact, 

even the levels immediately adjacent to 

the airguns may not be sufficient to 

induce PTS, especially since a mammal 

would not be exposed to more than one 

strong pulse unless it swam 

immediately alongside an airgun for a 

period longer than the inter-pulse 

interval (6–10 s). Baleen whales 

generally avoid the immediate area 

around operating seismic vessels. The 

planned monitoring and mitigation 

measures, including visual monitoring, 

ramp ups, and shut downs of the 

airguns when mammals are seen within 

the ‘‘safety radii’’, will minimize the 

already-minimal probability of exposure 

of marine mammals to sounds strong 

enough to induce PTS. 

Non-auditory Physiological Effects –

Non-auditory physiological effects or 

injuries that theoretically might occur in 

marine mammals exposed to strong 

underwater sound include stress, 

neurological effects, bubble formation, 

resonance effects, and other types of 

organ or tissue damage. There is no 

evidence that any of these effects occur 

in marine mammals exposed to sound 

from airgun arrays (even large ones) and 

there have been no direct studies of the 

potential for airgun pulses to elicit any 

of those effects. NMFS does not 

anticipate that marine mammals would 

experience any of these effects in 

response to being exposed to the airguns 

in this proposed study, especially 

considering the small size of the 

airguns. If any such effects do occur, 

they would probably be limited to 

unusual situations when animals might 

be exposed at close range for unusually 

long periods. 

Exposure of laboratory animals, 

wildlife, and humans to strong noise 

often results in significant increases in 

adrenal activity, including cortisol and/ 

or catecholamine release and related 

measures of stress (see Appendix A of 

SIO’s application). However, it is 

doubtful that any single marine 

mammal would be exposed to strong 

seismic sounds for sufficiently long that 

significant physiological stress would 

develop. That is especially so in the 

case of the present project where the 

airguns are small, the ship’s speed is 

relatively fast (5–8 knots or 9.3–14.8 

km/h), and each survey does not 

encompass a large area. 

Gas-filled structures in marine 

animals have an inherent fundamental 

resonance frequency. If stimulated at 

that frequency, the ensuing resonance 

could cause damage to the animal. A 

workshop (Gentry [ed.] 2002) was held 

to discuss whether the stranding of 

beaked whales in the Bahamas in 2000 

(Balcomb and Claridge, 2001; NOAA 

and USN, 2001) might have been related 

to air cavity resonance or bubble 

formation in tissues caused by exposure 

to noise from naval sonar. A panel of 

experts concluded that resonance in airfilled structures was not likely to have 

caused this stranding. Opinions were 

less conclusive about the possible role 

of gas (nitrogen) bubble formation/ 

growth in the Bahamas stranding of 

beaked whales. 

Until recently, it was assumed that 

diving marine mammals are not subject 

to the bends or air embolism. However, 

a short paper concerning beaked whales 

stranded in the Canary Islands in 2002 

suggests that cetaceans might be subject 

to decompression injury in some 

situations (Jepson et al., 2003). If so, that 

might occur if they ascend quickly 

when exposed to aversive sounds. 

However, the interpretation that the 

effect was related to decompression 

injury is unproven (Piantadosi and 

Thalmann 2004; Fernandez et al., 2004). 

Even if that effect can occur during 

exposure to mid-frequency sonar, there 

is no evidence that this type of effect 

occurs in response to airgun sounds. It 

is especially unlikely in the case of the 

proposed survey, involving only two GI 

guns. 

In general, little is known about the 

potential for seismic survey sounds to 

cause auditory impairment or other 

physical effects in marine mammals. 

Available data suggest that such effects, 

if they occur at all, would be limited to 

short distances and probably to projects 

involving large arrays of airguns. 

However, the available data do not 

allow for meaningful quantitative 

predictions of the numbers (if any) of 

marine mammals that might be affected 

in those ways. Marine mammals that 

show behavioral avoidance of seismic 

vessels, including most baleen whales, 

some odontocetes, and some pinnipeds, 

are especially unlikely to incur auditory 

impairment or other physical effects. 

Also, the planned mitigation measures, 

including ramp ups and shut downs, 

will reduce any such effects that might 

otherwise occur. 

Strandings and Mortality 

Marine mammals close to underwater 

detonations of high explosives can be 

killed or severely injured, and their 

auditory organs are especially 


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susceptible to injury (Ketten et al., 1993; 

Ketten 1995). Airgun pulses are less 

energetic and have slower rise times, 

and there is no proof that they can cause 

serious injury, death, or stranding even 

in the case of large airgun arrays. 

However, the association of several 

strandings of beaked whales with naval 

exercises and, in one case, an L-DEO 

seismic survey, has raised the 

possibility that beaked whales exposed 

to strong pulsed sounds may be 

especially susceptible to injury and/or 

behavioral reactions that can lead to 

stranding. Appendix A (g) of SIO’s 

application provides additional details. 

Seismic pulses and mid-frequency 

sonar pulses are quite different. Sounds 

produced by airgun arrays are 

broadband with most of the energy 

below 1 kHz. Typical military midfrequency sonars operate at frequencies 

of 2–10 kHz, generally with a relatively 

narrow bandwidth at any one time. 

Thus, it is not appropriate to assume 

that there is a direct connection between 

the effects of military sonar and seismic 

surveys on marine mammals. However, 

evidence that sonar pulses can, in 

special circumstances, lead to physical 

damage and mortality (NOAA and USN 

2001; Jepson et al., 2003), even if only 

indirectly, suggests that caution is 

warranted when dealing with exposure 

of marine mammals to any highintensity pulsed sound. 

In May 1996, 12 Cuvier’s beaked 

whales stranded along the coasts of 

Kyparissiakos Gulf in the Mediterranean 

Sea. That stranding was subsequently 

linked to the use of low- and mediumfrequency active sonar by a North 

Atlantic Treaty Organization (NATO) 

research vessel in the region (Frantzis 

1998). In March 2000, a population of 

Cuvier’s beaked whales being studied in 

the Bahamas disappeared after a U.S. 

Navy task force using mid-frequency 

tactical sonars passed through the area; 

some beaked whales stranded (Balcomb 

and Claridge, 2001; NOAA and USN, 

2001). 

In September 2002, a total of 14 

beaked whales of various species 

stranded coincident with naval 

exercises in the Canary Islands (Martel 

n.d.; Jepson et al., 2003; Fernandez et 

al., 2003). Also in Sept. 2002, there was 

a stranding of two Cuvier’s beaked 

whales in the Gulf of California, Mexico, 

when the L-DEO vessel Maurice Ewing 

was operating a 20–gun, 8490–in3 array 

in the general area. The link between 

the stranding and the seismic surveys 

was inconclusive and not based on any 

physical evidence (Hogarth, 2002; 

Yoder, 2002). Nonetheless, that plus the 

incidents involving beaked whale 

strandings near naval exercises suggests 

a need for caution in conducting seismic 

surveys in areas occupied by beaked 

whales. 

The present project will involve a 

much smaller sound source than used in 

typical seismic surveys. That, along 

with the monitoring and mitigation 

measures that are planned, are expected 

to minimize any possibility for 

strandings and mortality. 

Potential Effects of Other Acoustic 

Devices 

Bathymetric Sonar Signals 

A multi-beam bathymetric sonar 

(Simrad EM120, 11.25–12.6 kHz) will be 

operated from the source vessel during 

much of the planned study. Sounds 

from the multi-beam sonar are very 

short pulses. Most of the energy in the 

sound pulses emitted by the multi-beam 

is at moderately high frequencies, 

centered at 12 kHz. The beam is narrow 

(1° or 2°) in fore-aft extent, and wide 

(150°) in the cross-track extent. Each 

ping consists of nine successive 

transmissions (segments) at different 

cross-track angles. Any given mammal 

at depth near the track line would be in 

the main beam for only a fraction of a 

second. 

Tactical Navy sonars that have been 

linked to avoidance reactions and 

stranding of cetaceans (1) generally are 

more powerful than the Simrad EM120, 

(2) have a longer pulse duration, and (3) 

are directed close to omnidirectionally, 

vs. downward for the Simrad EM120. 

The area of possible influence of the 

Simrad EM120 is a much smaller 

narrow band oriented in the cross-track 

direction below the source vessel. 

Marine mammals that encounter the 

Simrad EM120 at close range are 

unlikely to be subjected to repeated 

pulses because of the narrow fore-aft 

width of the beam, and will receive only 

limited amounts of pulse energy 

because of the short pulses. In assessing 

the possible impacts of the 15.5 kHz 

Atlas Hydrosweep (a similar model), 

Boebel et al. (2004) noted that the 

critical sound pressure level at which 

TTS may occur is 203.2 dB re 1 μPa 

(rms). The critical region included an 

area of 43 m (141 ft) in depth, 46 m (151 

ft) wide athwartship, and 1 m (3.3 ft) 

fore-and-aft (Boebel et al., 2004). 

Behavioral reactions of free-ranging 

marine mammals to military and other 

sonars appear to vary by species and 

circumstance. Observed reactions have 

included silencing and dispersal by 

sperm whales (Watkins et al., 1985), 

increased vocalizations and no dispersal 

by pilot whales (Rendell and Gordon, 

1999), and the previously-mentioned 

beachings by beaked whales. However, 

all of those observations are of limited 

relevance to the present situation. Pulse 

durations from those sonars were much 

longer than those of the SIO multi-beam 

sonar, and a given mammal would have 

received many pulses from the naval 

sonars. During SIO’s operations, the 

individual pulses will be very short, and 

a given mammal would not receive 

many of the downward-directed pulses 

as the vessel passes by. 

Captive bottlenose dolphins and a 

white whale exhibited changes in 

behavior when exposed to 1 s pulsed 

sounds at frequencies similar to those 

that will be emitted by the multi-beam 

sonar used by SIO, and to shorter 

broadband pulsed signals. Behavioral 

changes typically involved what 

appeared to be deliberate attempts to 

avoid the sound exposure (Schlundt et 

al., 2000; Finneran et al., 2002). The 

relevance of those data to free-ranging 

odontocetes is uncertain, and in any 

case, the test sounds were quite 

different in either duration or 

bandwidth as compared with those from 

a bathymetric sonar. 

Because of the shape of the beam, 

NMFS believes it unlikely that marine 

mammals will be exposed to the 

bathymetric sonar at levels at or above 

those likely to cause harassment. 

Further, NMFS believes that the brief 

exposure of cetaceans or pinnipeds to 

one pulse, or small numbers of signals, 

from the multi-beam bathymetric sonar 

system are not likely to result in the 

harassment of marine mammals. 

Sub-bottom Profiler Signals 

A sub-bottom profiler will be operated 

from the source vessel at all times 

during the planned study. Sounds from 

the sub-bottom profiler are very short 

pulses, occurring for 12 or 24 ms once 

every 4.5–8 seconds. Most of the energy 

in the sound pulses emitted by this subbottom profiler is at mid frequencies, 

centered at 3.5 kHz. The beam width is 

approximately 80o (cone-shaped) and is 

directed downward. 

The sub-bottom profiler on the Roger 

Revelle has a stated maximum source 

level of 211 dB re 1 μPa m (see section 

I of SIO’s application). Thus, the 

received level would be expected to 

decrease to 180 dB and 160 dB 

approximately 35 m and 350 m below 

the transducer, respectively, assuming 

spherical spreading. Corresponding 

distances in the horizontal plane would 

be substantially lower, given the 

directionality of this source. 

Marine mammal behavioral reactions 

to other pulsed sound sources are 

discussed above, and responses to the 

sub-bottom profiler are likely to be 

similar to those for other pulsed sources 


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if received at the same levels. However, 

the pulsed signals from the sub-bottom 

profiler are weaker than those from both 

the multi-beam sonar and the two GI 

guns. Behavioral responses are not 

expected unless marine mammals are 

very close to the source, e.g., within 

approximately 350 m below the vessel, 

or a lesser distance to the side. It is 

unlikely that the sub-bottom profiler 

produces pulse levels strong enough to 

cause hearing impairment or other 

physical injuries even in an animal that 

is (briefly) in a position near the source. 

The sub-bottom profiler is usually 

operated simultaneously with other 

higher-power acoustic sources. Many 

marine mammals will move away in 

response to the approaching higherpower sources or the vessel itself before 

the mammals would be close enough for 

there to be any possibility of effects 

from the less intense sounds from the 

sub-bottom profiler. In the case of 

mammals that do not avoid the 

approaching vessel and its various 

sound sources, mitigation measures that 

would be applied to minimize effects of 

the higher-power sources would further 

reduce or eliminate any minor effects of 

the sub-bottom profiler. 

Because of the shape of the conical 

beam and the power of the source, 

NMFS believes it unlikely that marine 

mammals will be exposed to the 

bathymetric sonar at levels at or above 

those likely to cause harassment. 

Further, NMFS believes that the brief 

exposure of cetaceans or pinnipeds to 

small numbers of signals from the multibeam bathymetric sonar system are not 

likely to result in the harassment of 

marine mammals. 

Estimated Take by Incidental 

Harassment 

All anticipated takes would be ‘‘takes 

by harassment’’, involving temporary 

changes in behavior. The proposed 

mitigation measures are expected to 

minimize the possibility of injurious 

takes. (However, as noted earlier, there 

is no specific information demonstrating 

that injurious ‘‘takes’’ would occur even 

in the absence of the planned mitigation 

measures.) In the sections below, we 

describe methods to estimate ‘‘take by 

harassment’’, and present estimates of 

the numbers of marine mammals that 

might be affected during the proposed 

seismic survey in the northeast Indian 

Ocean. The estimates are based on the 

best available data concerning marine 

mammal densities (numbers per unit 

area) and estimates of the size of the 

area where effects potentially could 

occur. 

Because there is very little 

information on marine mammal 

densities in the proposed survey area, 

densities were used from two of 

Longhurst’s (2007) biogeographic 

provinces in the ETP that are 

oceanographically similar to the two 

provinces in which the seismic 

activities will take place (see further, 

below). 

SIO’s application presents two types 

of estimates: estimates of the number of 

potential ‘‘exposures’’, and estimates of 

the number of different individual 

marine mammals that might potentially 

be exposed to sound levels ≥160 dB re 

1 μPa (rms). The distinction between 

‘‘exposures’’ and ‘‘number of different 

individuals exposed’’ is marginally 

relevant in this project, because the plan 

does not call for repeated GI gun 

operations through the same or adjacent 

waters, and the 2 GI guns that will be 

used ensonify a relatively small area. 

Estimates of the number of exposures 

are considered precautionary 

overestimates of the actual numbers of 

different individuals potentially 

exposed to seismic sounds, because in 

all likelihood, exposures represent 

repeated exposures of some of the same 

individuals as discussed in the sections 

that follow. Because of their 

precautionary nature, the fact that they 

are the numbers SIO requested 

authorization for, and the fact that they 

differ only slightly from the estimated 

number of individuals, NMFS will use 

the estimated number of exposures for 

the take estimate. 

The following estimates are based on 

a consideration of the number of marine 

mammals that might be disturbed 

appreciably by operations with the 2 GI 

guns to be used during approximately 

2700 line-km of surveys at five sites on 

the Ninety East Ridge in the 

northeastern Indian Ocean. The 

anticipated radii of influence of the 

multi-beam sonar and sub-bottom 

profiler are less than those for the GI 

guns. It is assumed that, during 

simultaneous operations of the multibeam sonar and airguns, any marine 

mammals close enough to be affected by 

the sonar would already be affected by 

the airguns. No animals are expected to 

exhibit more than short-term and 

inconsequential responses to the multibeam sonar and sub-bottom profiler, 

given their characteristics (e.g., narrow 

downward-directed beam) and other 

considerations described previously. 

Therefore, no additional allowance is 

included for animals that might be 

affected by those sources. Any effects of 

the multi-beam sonar and sub-bottom 

profiler during times when they are 

operating but the airguns are silent are 

not considered. 

Few systematic aircraft- or ship-based 

surveys have been conducted for marine 

mammals in offshore waters of the 

Indian Ocean, and the species of marine 

mammals that occur there are not well 

known. The density estimates used in 

this assessment are from two sources, as 

noted above. The most comprehensive 

and recent density data available for 

cetaceans of the ETP are from 1986 1996 

NMFS ship surveys reported by 

Ferguson and Barlow (2001). 

(1) Some of those waters are in 

Longhurst’s (2007) Pacific Equatorial 

Divergence Province (PEQD), which is 

similar to the Indian Monsoon Gyres 

Province (MONS), in which 3 of the 5 

proposed seismic surveys in the 

northeastern Indian Ocean will occur. 

The similarities are that they are both 

high-nitrate, low-chlorophyll regions of 

the oceans that support relatively large 

populations of yellowfin, bigeye, and 

skipjack tuna. SIO used the 1986 1996 

data from blocks 162–170, 202–209, and 

213–216 of Ferguson and Barlow (2001) 

for the species group density estimates 

given in Table 3 of SIO’s application 

(and used to calculate the take estimates 

in Table 1 here). 

(2) Some of the surveys conducted by 

Ferguson and Barlow (2001) in the ETP 

are in Longhurst’s (2007) North Pacific 

Tropical Gyre Province (NPTG), which 

is similar to the Indian South 

Subtropical Gyre Province (ISSG), in 

which 2 of the 5 proposed seismic 

surveys will occur. The similarities are 

that they are both low-nitrate, lowchlorophyll regions of the oceans that 

support relatively large bigeye and 

yellowfin tuna populations. SIO used 

the 1986 1996 data from blocks 105, 

106, 111, 112, and 125 131 of Ferguson 

and Barlow (2001) to compute the 

species group densities in Table 4 of 

their application (and used to calculate 

the take estimates in Table 1 here). 

The species that will be encountered 

during the Indian Ocean survey will be 

different than those sighted during the 

surveys in the ETP. However, the 

overall abundance of species groups 

with generally similar habitat 

requirements are expected to be roughly 

similar. No density data were available 

for any cetacean species in the proposed 

seismic survey area. Thus, data from 

offshore areas of the ETP to estimate the 

densities of beaked whales, delphinids, 

small whales, and mysticetes in the 

northeastern Indian Ocean were used. 

SIO then estimated the relative 

abundance of individual species within 

the species groups on a scale of 1 (rare) 

to 10 (abundant) using various surveys 

and other information from areas near 

the study area, and general information 

on species such as latitudinal ranges, 


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water depth preferences, and group 

sizes (see Column 1 in Tables 3 and 4 

of SIO’s application). Finally, SIO 

estimated the density of each species 

expected to occur in the survey area 

from the densities for species groups in 

Tables 3 and 4 of their application by 

multiplying their relative abundance/ 

the relative abundance for all species in 

the species group times the density for 

the species group. 

Tables 3 and 4 in SIO’s application 

give the average and maximum densities 

for each species group of marine 

mammals reported in the PEQD and 

NPTG provinces of the ETP, corrected 

for effort, based on the densities 

reported in Ferguson and Barlow (2001). 

The densities from those studies had 

been corrected, by the original authors, 

for both detectability bias and 

availability bias. Detectability bias is 

associated with diminishing sightability 

with increasing lateral distance from the 

track line [f(0)]. Availability bias refers 

to the fact that there is less-than 100 

percent probability of sighting an 

animal that is present along the survey 

track line, and it is measured by g(0). 

It should be noted that the following 

estimates of ‘‘takes by harassment’’

assume that the seismic surveys will be 

undertaken and completed; in fact, the 

planned number of line-kms has been 

increased by 25 percent to accommodate 

lines that may need to be repeated, 

equipment testing, etc. As is typical on 

offshore ship surveys, inclement 

weather, equipment malfunctions, and 

other survey priorities (rock dredging, 

magnetic surveys) may cause delays and 

may limit the number of useful line-kms 

of seismic operations that can be 

undertaken. Furthermore, any marine 

mammal sightings within or near the 

designated safety zones will result in 

the shut down of seismic operations as 

a mitigation measure. Thus, the 

following estimates of the numbers of 

marine mammals potentially exposed to 

160–dB sounds are precautionary, and 

probably overestimate the actual 

numbers of marine mammals that might 

be involved. The estimates assume that 

there are no conflicts in survey 

priorities or weather, equipment, or 

mitigation delays, which is unlikely, 

particularly given the complexity of the 

tasks and equipment involved. 

There is some uncertainty about the 

representativeness of the data and the 

assumptions used in the take 

calculations. However, the approach 

used here is believed to be the best 

available approach. Also, to provide 

some allowance for the uncertainties, 

‘‘maximum estimates’’ as well as ‘‘best 

estimates’’ of the numbers potentially 

affected have been derived. Best and 

maximum estimates are based on the 

average and maximum estimates of 

densities reported in the selected 

datasets that were used from Ferguson 

and Barlow (2001) described above. SIO 

has requested authorization for the take 

of the maximum estimates and NMFS 

has analyzed the maximum estimate for 

it’s effect on the species or stock. 

The potential number of occasions 

when members of each species might be 

exposed to received levels ≥160 dB re 1 

μPa (rms) was calculated by multiplying 

• Its expected density, either 

‘‘average’’ (i.e., best) or ‘‘maximum’’, 

corrected as described above, times 

• The anticipated total linekilometers of operations with the 2 GI 

guns (including turns and additional 

buffer line km to allow for repeating of 

lines due to equipment malfunction, 

bad weather, etc.), times 

• The cross-track distances within 

which received sound levels are 

predicted to be ≥160 dB. 

For the 2 GI guns, that cross track 

distance is 2x the predicted 160–dB 

radii of 400 m (1312 ft) in water depths 

>1000 m (3280 ft). 

Based on that method, the ‘‘best’’ and 

‘‘maximum’’ estimates of the number of 

marine mammal exposures to airgun 

sounds ≥160 dB re 1 μPa (rms) were 

obtained for each of the ecological 

provinces using the reported average 

and maximum densities from Tables 3 

and 4 of SIO’s application. The two 

estimates were then added to give totals. 

Of the five endangered cetacean species 

that could be present, the best and 

maximum estimates show that only one 

blue whale and one sperm whale may 

be exposed to such noise levels (Table 

5 of SIO’s application). The vast 

majority of the best and maximum 

exposures to seismic sounds ≥160 dB 

would involve delphinids. Maximum 

estimates of exposures for the species 

with the highest numbers are, in 

descending order, spinner dolphin (215 

exposures), common and Risso’s 

dolphins (151 exposures), and 

bottlenose dolphin (129 exposures). 

Estimates for other species are lower 

(Table 1). 

The far right column in Table 1, 

‘‘Requested Take Authorization’’, shows 

the numbers for which ‘‘take 

authorization’’ is requested. The 

requested take authorization numbers 

are calculated as indicated above based 

on the maximum densities reported by 

Ferguson and Barlow (2001) in any of 

the survey blocks included in the 

average density estimates. For those 

species for which very low numbers to 

none are estimated to be exposed to 

seismic sounds ≥160 dB, SIO included 

allowance for encountering one group 

based on the mean group size. Where 

group sizes are less than five, SIO 

assigned a group size of five. However, 

for endangered species, NMFS only 

plans to authorize take for one sperm 

whale and one blue whale. 

The best and maximum estimates are 

based on 160–dB distances predicted 

from the acoustic model applied by LDEO. Based on the empirical calibration 

data collected in the Gulf of Mexico in 

2003 for L-DEO’s 2 GI guns in deep 

water (510 m (1673 ft)), actual 160–dB 

distances in deep water are likely to be 

less than predicted (Tolstoy et al., 

2004). Additionally, the requested take 

is based on maximum exposure 

estimates (based on maximum density 

estimates). Given these considerations, 

the predicted numbers of marine 

mammals that might be exposed to 

sounds ≥160 dB may be somewhat 

overestimated. 

The stock structures of the marine 

mammals present in the Indian Ocean 

have not been identified by NMFS; 

therefore, NMFS must make the 

necessary findings based on the species 

as a whole. The species anticipated to 

be affected during the proposed 

activities are wide-ranging species. 

Though worldwide abundance (or 

abundance outside of that estimated for 

the U.S. stocks) has not been estimated, 

localized surveys in the west tropical 

Indian Ocean and elsewhere have been 

conducted. Since the take estimates 

proposed in this document fall largely 

within 6 percent (all but common 

dolphin (21 percent) and rough-toothed 

dolphin (14 percent)) of the numbers 

estimated to be present during a 

localized survey of the west tropical 

Indian Ocean, and the species range far 

beyond the Indian Ocean (i.e., the 

abundance of the species is notably 

larger), NMFS believes that the 

estimated take numbers for these are 

small relative both to the worldwide 

abundance of these species and to 

numbers taken in other activities that 

have been authorized for incidental take 

of these species. 

Potential Effects on Habitat 

The proposed airgun operations will 

not result in any permanent impact on 

habitats used by marine mammals, or to 

the food sources they use. The main 

impact issue associated with the 

proposed activities will be temporarily 

elevated noise levels and the associated 

direct effects on marine mammals, as 

discussed above. 

One of the reasons for the adoption of 

airguns as the standard energy source 

for marine seismic surveys was that they 

(unlike the explosives used in the 

distant past) do not result in any 


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appreciable fish kill. However, the 

existing body of information relating to 

the impacts of seismic on marine fish 

and invertebrate species is very limited. 

The various types of potential effects of 

exposure to seismic on fish and 

invertebrates can be considered in three 

categories: (1) pathological, (2) 

physiological, and (3) behavioral. 

Pathological effects include lethal and 

sub-lethal damage to the animals, 

physiological effects include temporary 

primary and secondary stress responses, 

and behavioral effects refer to changes 

in exhibited behavior of the fish and 

invertebrates. The three categories are 

interrelated in complex ways. For 

example, it is possible that certain 

physiological and behavioral changes 

could potentially lead to the ultimate 

pathological effect on individual 

animals (i.e., mortality). 

The available information on the 

impacts of seismic surveys on marine 

fish and invertebrates provides limited 

insight on the effects only at the 

individual level. Ultimately, the most 

important knowledge in this area relates 

to how significantly seismic affects 

animal populations. 

The following sections provide an 

overview of the information that exists 

on the effects of seismic surveys on fish 

and invertebrates. The information 

comprises results from scientific studies 

of varying degrees of soundness and 

some anecdotal information. 

Pathological Effects – In water, acute 

injury and death of organisms exposed 

to seismic energy depends primarily on 

two features of the sound source: (1) the 

received peak pressure, and (2) the time 

required for the pressure to rise and 

decay (Hubbs and Rechnitzer, 1952 in 

Wardle et al., 2001). Generally, the 

higher the received pressure and the 

less time it takes for the pressure to rise 

and decay, the greater the chance of 

acute pathological effects. Considering 

the peak pressure and rise/decay time 

characteristics of seismic airgun arrays 

used today, the pathological zone for 

fish and invertebrates would be 

expected to be within a few meters of 

the seismic source (Buchanan et al., 

2004). For the proposed survey, any 

injurious effects on fish would be 

limited to very short distances, 

especially considering the small source 

planned for use in this project (two 45–

in3 GI guns). 

Matishov (1992) reported that some 

cod and plaice died within 48 hours of 

exposure to seismic pulses 2 m (6.5 ft) 

from the source. No other details were 

provided by the author. On the other 

hand, there are numerous examples of 

no fish mortality as a result of exposure 

to seismic sources (Falk and Lawrence 

1973; Holliday et al., 1987; La Bella et 

al., 1996; Santulli et al., 1999; McCauley 

et al., 2000a, 2000b; Bjarti, 2002; IMG, 

2002; McCauley et al., 2003; Hassel et 

al., 2003). 

There are examples of damage to fish 

ear structures from exposure to seismic 

airguns (McCauley et al., 2000a, 2000b, 

2003), but it should be noted the 

experimental fish were caged and 

exposed to high cumulative levels of 

seismic energy. Atlantic salmon were 

exposed within 1.5 m (4.9 ft) of 

underwater explosions (Sverdrup et al., 

1994). Compared to airgun sources, 

explosive detonations are characterized 

by higher peak pressures and more 

rapid rise and decay times, and are 

considered to have greater potential to 

damage marine biota. In spite of this, no 

salmon mortality was observed 

immediately after exposure or during 

the seven-day monitoring period 

following exposure. 

Some studies have also provided 

some information on the effects of 

seismic exposure on fish eggs and larvae 

(Kostyuchenko, 1972; Dalen and 

Knutsen, 1986; Holliday et al., 1987; 

Matishov, 1992; Booman et al., 1996; 

Dalen et al., 1996). Overall, impacts 

appeared to be minimal and any 

mortality was generally not significantly 

different from the experimental 

controls. Generally, any observed larval 

mortality occurred after exposures 

within 0.5 3 m (1.6–9.8 ft) of the airgun 

source. Matishov (1992) did report some 

retinal tissue damage in cod larvae 

exposed at 1 m (3.3 ft) from the airgun 

source. Saetre and Ona (1996) applied a 

’worst-case scenario’ mathematical 

model to investigate the effects of 

seismic energy on fish eggs and larvae, 

and concluded that mortality rates 

caused by exposure to seismic are so 

low compared to natural mortality that 

the impact of seismic surveying on 

recruitment to a fish stock must be 

regarded as insignificant. 

The pathological impacts of seismic 

energy on marine invertebrate species 

have also been investigated. Christian et 

al. (2003) exposed adult male snow 

crabs, egg-carrying female snow crabs, 

and fertilized snow crab eggs to energy 

from seismic airguns. Neither acute nor 

chronic (12 weeks after exposure) 

mortality was observed for the adult 

male and female crabs. There was a 

significant difference in development 

rate noted between the exposed and 

unexposed fertilized eggs. The egg mass 

exposed to seismic energy had a higher 

proportion of less-developed eggs than 

the unexposed mass. It should be noted 

that both egg masses came from a single 

female and that any measure of natural 

variability was unattainable. However, a 

result such as this does point to the 

need for further study. 

Pearson et al. (1994) exposed Stage II 

larvae of the Dungeness crab to single 

discharges from a seven-airgun seismic 

array and compared their mortality and 

development rates with those of 

unexposed larvae. For immediate and 

long-term survival and time to molt, this 

field experiment did not reveal any 

statistically-significant differences 

between the exposed and unexposed 

larvae, even those exposed within 1 m 

(3.3 ft) of the seismic source. 

Bivalves of the Adriatic Sea were also 

exposed to seismic energy and 

subsequently assessed (LaBella et al., 

1996). No effects of the exposure were 

noted. 

To date, there have not been any welldocumented cases of acute post-larval 

fish or invertebrate mortality as a result 

of exposure to seismic sound under 

normal seismic operating conditions. 

Sub-lethal injury or damage has been 

observed, but generally as a result of 

exposure to very high received levels of 

sound, significantly higher than the 

received levels generated by the single 

GI gun sound source to be used in the 

proposed study. Acute mortality of eggs 

and larvae have been demonstrated in 

experimental exposures, but only when 

the eggs and larvae were exposed very 

close to the seismic sources and the 

received pressure levels were 

presumably very high. Limited 

information has not indicated any 

chronic mortality as a direct result of 

exposure to seismic. 

Physiological Effects – Biochemical 

responses by marine fish and 

invertebrates to acoustic stress have also 

been studied, although in a limited way. 

Studying the variations in the 

biochemical parameters influenced by 

acoustic stress might give some 

indication of the extent of the stress and 

perhaps forecast eventual detrimental 

effects. Such stress could potentially 

affect animal populations by reducing 

reproductive capacity and adult 

abundance. 

McCauley et al. (2000a, 2000b) used 

various physiological measures to study 

the physiological effects of exposure to 

seismic energy on various fish species, 

squid, and cuttlefish. No significant 

physiological stress increases 

attributable to seismic energy were 

detected. Sverdrup et al. (1994) found 

that Atlantic salmon subjected to 

acoustic stress released primary stress 

hormones, adrenaline and cortisol, as a 

biochemical response although there 

were different patterns of delayed 

increases for the different indicators. 

Caged European sea bass were exposed 

to seismic energy and numerous 


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biochemical responses were indicated. 

All returned to their normal 

physiological levels within 72 hours of 

exposure. 

Stress indicators in the haemolymph 

of adult male snow crabs were 

monitored after exposure of the animals 

to seismic energy (Christian et al., 

2003). No significant differences 

between exposed and unexposed 

animals were found in the stress 

indicators (e.g., proteins, enzymes, cell 

type count). 

Primary and secondary stress 

responses of fish after exposure to 

seismic energy all appear to be 

temporary in any studies done to date. 

The times necessary for these 

biochemical changes to return to normal 

are variable depending on numerous 

aspects of the biology of the species and 

of the sound stimulus. 

Summary of Physical (Pathological 

and Physiological) Effects – As 

indicated in the preceding general 

discussion, there is a relative lack of 

knowledge about the potential physical 

(pathological and physiological) effects 

of seismic energy on marine fish and 

invertebrates. Available data suggest 

that there may be physical impacts on 

egg, larval, juvenile, and adult stages at 

very close range. Considering typical 

source levels associated with 

commercial seismic arrays, close 

proximity to the source would result in 

exposure to very high energy levels. 

Again, this study will employ a sound 

source that will generate low energy 

levels. Whereas egg and larval stages are 

not able to escape such exposures, 

juveniles and adults most likely would 

avoid it. In the case of eggs and larvae, 

it is likely that the numbers adversely 

affected by such exposure would not be 

that different from those succumbing to 

natural mortality. Limited data 

regarding physiological impacts on fish 

and invertebrates indicate that these 

impacts are short term and are most 

apparent after exposure at close range. 

The proposed seismic program for 

2007 is predicted to have negligible to 

low physical effects on the various life 

stages of fish and invertebrates for its 

short duration (approximately 49 hours 

at each of five sites on the Ninety East 

Ridge) and 2700–km extent. Therefore, 

physical effects of the proposed program 

on the fish and invertebrates would be 

not significant. 

Fish and Invertebrate Acoustic 

Detection and Production – Hearing in 

fishes was first demonstrated in the 

early 1900s through studies involving 

cyprinids (Parker, 1903 and Bigelow, 

1904 in Kenyon et al., 1998). Since that 

time, numerous methods have been 

used to test auditory sensitivity in 

fishes, resulting in audiograms of over 

50 species. These data reveal great 

diversity in fish hearing ability, mostly 

attributable to various peripheral modes 

of coupling the ear to internal 

structures, including the swim bladder. 

However, the general auditory 

capabilities of <0.2 percent of fish 

species are known so far. 

For many years, studies of fish 

hearing have reported that the hearing 

bandwidth typically extends from below 

100 Hz to approximately 1 kHz in fishes 

without specializations for sound 

detection, and up to approximately 7 

kHz in fish with specializations that 

enhance bandwidth and sensitivity. 

Recently there have been suggestions 

that certain fishes, including many 

clupeiforms (herring, shads, anchovies, 

etc.) may be capable of detecting 

ultrasonic signals with frequencies as 

high as 126 kHz (Dunning et al., 1992; 

Nestler et al., 1992). Studies on Atlantic 

cod, a non-clupeiform fish, suggested 

that this species could detect ultrasound 

at almost 40 kHz (Astrup and M hl, 

1993). 

Mann et al. (2001) showed that the 

American shad is capable of detecting 

sounds up to 180 kHz. They also 

demonstrated that the gulf menhaden is 

also able to detect ultrasound, whereas 

other species such as the bay anchovy, 

scaled sardine, and Spanish sardine 

only detect sounds with frequencies up 

to approximately 4 kHz. 

Among fishes, at least two major 

pathways for sound transmission to the 

ear have been identified. The first and 

most primitive is the conduction of 

sound directly from the water to tissue 

and bone. The fish’s body takes up the 

sound’s acoustic particle motion and 

subsequent hair cell stimulation occurs 

because of the difference in inertia 

between the hair cells and their 

overlying otoliths. These species are 

known as ’hearing generalists’ (Fay and 

Popper, 1999). The second sound 

pathway to the ears is indirect. The 

swim bladder or other gas bubble near 

the ears expands and contracts in 

volume in response to sound pressure 

fluctuations, and the motion is then 

transmitted to the otoliths. While 

present in most bony fishes, the swim 

bladder is absent or reduced in many 

other fish species. Only some species of 

fish with a swim bladder appear to be 

sound-pressure sensitive via this 

indirect pathway to the ears; they are 

called ’hearing specialists’. Hearing 

specialists have some sort of connection 

with the inner ear, either via bony 

structures known as Weberian ossicles, 

extensions of the swim bladder, or a 

swim bladder more proximate to the 

inner ear. Hearing specialists’ soundpressure sensitivity is high and their 

upper frequency range of detection is 

extended above those species that hear 

only by the direct pathway. Typically, 

most fish detect sounds of frequencies 

up to 2,000–Hz but, as indicated, others 

have detection ranges that extend to 

much higher frequencies. 

Fish also possess lateral lines that 

detect water movements. The essential 

stimulus for the lateral line consists of 

differential water movement between 

the body surface and the surrounding 

water. The lateral line is typically used 

in concert with other sensory 

information, including hearing (Sand, 

1981; Coombs and Montgomery, 1999). 

Elasmobranchs (sharks and skates) 

lack any known pressure-todisplacement transducers such as swim 

bladders. Therefore, they presumably 

must rely on the displacement 

sensitivity of their mechanoreceptive 

cells. Unlike acoustic pressure, the 

kinetic stimulus is inherently 

directional but its magnitude rapidly 

decreases relative to the pressure 

component as it propagates outward 

from the sound source in the near field. 

It is believed that elasmobranches are 

most sensitive to low frequencies, those 

<1 kHz (Corwin 1981). 

Because they lack air-filled cavities 

and are often the same density as water, 

invertebrates detect underwater 

acoustics differently than fish. Rather 

than being pressure sensitive, 

invertebrates appear to be most sensitive 

to particle displacement. However, their 

sensitivity to particle displacement and 

hydrodynamic stimulation seem poor 

compared to fish. Decapods, for 

example, have an extensive array of 

hair-like receptors both within and 

upon the body surface that could 

potentially respond to water- or 

substrate-borne displacements. They are 

also equipped with an abundance of 

proprioceptive organs that could serve 

secondarily to perceive vibrations. 

Crustaceans appear to be most sensitive 

to sounds of low frequencies, those 

<1000 Hz (Budelmann, 1992; Popper et 

al., 2001). 

Many fish and invertebrates are also 

capable of sound production. It is 

believed that these sounds are used for 

communication in a wide range of 

behavioral and environmental contexts. 

The behaviors most often associated 

with acoustic communication include 

territorial behavior, mate finding, 

courtship, and aggression. Sound 

production provides a means of longdistance communication and 

communication when underwater 

visibility is poor (Zelick et al., 1999). 

Behavioral Effects – Because of the 

apparent lack of serious pathological 


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17862 Federal Register / Vol. 72, No. 68 / Tuesday, April 10, 2007 / Notices 

and physiological effects of seismic 

energy on marine fish and invertebrates, 

most concern now centers on the 

possible effects of exposure to seismic 

surveys on the distribution, migration 

patterns, and catchability of fish. There 

is a need for more information on 

exactly what effects such sound sources 

might have on the detailed behavior 

patterns of fish and invertebrates at 

different ranges. Studies investigating 

the possible effects of seismic energy on 

fish and invertebrate behavior have been 

conducted on both uncaged and caged 

animals. Studies of change in catch rate 

regard potential effects of seismic 

energy on larger spatial and temporal 

scales than are typical for close-range 

studies that often involve caged animals 

(Hirst and Rodhouse, 2000). Hassel et al. 

(2003) investigated the behavioral 

effects of seismic pulses on caged sand 

lance in Norwegian waters. The sand 

lance did exhibit responses to the 

seismic, including an increase in 

swimming rate, an upwards vertical 

shift in distribution, and startle 

responses. Normal behaviors were 

resumed shortly after cessation of the 

seismic source. None of the observed 

sand lance reacted by burying into the 

sand. 

Engas et al. (1996) assessed the effects 

of seismic surveying on Atlantic cod 

and haddock behavior using acoustic 

mapping and commercial fishing 

techniques. Results indicated that fish 

abundance decreased at the seismic 

survey area, and that the decline in 

abundance and catch rate lessened with 

distance from the survey area. Fish 

abundance and catch rates had not 

returned to pre-shooting levels five days 

after cessation of shooting. In other 

airgun experiments, catch per unit effort 

(CPUE) of demersal fish declined when 

airgun pulses were emitted, particularly 

in the immediate vicinity of the seismic 

survey (Dalen and Raknes, 1985; Dalen 

and Knutsen, 1986; L kkeborg, 1991; 

Skalski et al., 1992). Reductions in the 

catch may have resulted from a change 

in behavior of the fish. The fish schools 

descended to near the bottom when the 

airgun was firing, and the fish may have 

changed their swimming and schooling 

behavior. Fish behavior returned to 

normal minutes after the sounds ceased. 

Marine fish inhabiting an inshore reef 

off the coast of Scotland were monitored 

by telemetry and remote camera before, 

during, and after airgun firing (Wardle 

et al., 2001). Although some startle 

responses were observed, the seismic 

gun firing had little overall effect on the 

day-to-day behavior of the resident fish. 

Other species involved in studies that 

have indicated fish behavioral responses 

to underwater sound include rockfish 

(Pearson et al., 1992), Pacific herring 

(Schwarz and Greer, 1984), and Atlantic 

herring (Blaxter et al., 1981). The 

responses observed in these studies 

were relatively temporary. What is not 

known is the effect of exposure to 

seismic energy on fish and invertebrate 

behaviors that are associated with 

reproduction and migration. 

Studies on the effects of sound on fish 

behavior have also been conducted 

using caged or confined fish. Such 

experiments were conducted in 

Australia using fish, squid, and 

cuttlefish as subjects (McCauley et al. 

(2000a,b). Common observations of fish 

behavior included startle response, 

faster swimming, movement to the part 

of the cage furthest from the seismic 

source (i.e., avoidance), and eventual 

habituation. Fish behavior appeared to 

return pre-seismic state 15 30 min after 

cessation of seismic shooting. Squid 

exhibited strong startle responses to the 

onset of proximate airgun firing by 

releasing ink and/or jetting away from 

the source. The squid consistently made 

use of the ’sound shadow’ at the surface, 

where the sound intensity was less than 

at 3–m (9.8 ft) depth. These Australian 

experiments provided more evidence 

that fish and invertebrate behavior will 

be modified at some received sound 

level. Again, the behavioral changes 

seem to be temporary. 

Christian et al. (2003) conducted an 

experimental commercial fishery for 

snow crab before and after the area was 

exposed to seismic shooting. Although 

the resulting data were not conclusive, 

no drastic decrease in catch rate was 

observed after seismic shooting 

commenced. Another behavioral 

investigation by Christian et al. (2003) 

involved caging snow crabs, positioning 

the cage 50 m (164 ft) below a seven-gun 

array, and observing the immediate 

responses of the crabs to the onset of 

seismic shooting by remote underwater 

camera. No obvious startle behaviors 

were observed. Anecdotal information 

from Newfoundland, Canada, indicated 

that snow crab catch rates showed a 

significant reduction immediately 

following a pass by a seismic survey 

vessel. Other anecdotal information 

from Newfoundland indicated that a 

school of shrimp showing on a fishing 

vessel sounder shifted downwards and 

away from a nearby seismic source. 

Effects were temporary in both the snow 

crab and shrimp anecdotes (Buchanan et 

al., 2004). 

Summary of Behavioral Effects – As is 

the case with pathological and 

physiological effects of seismic on fish 

and invertebrates, available information 

is relatively scant and often 

contradictory. There have been welldocumented observations of fish and 

invertebrates exhibiting behaviors that 

appeared to be responses to exposure to 

seismic energy (i.e., startle response, 

change in swimming direction and 

speed, and change in vertical 

distribution), but the ultimate 

importance of those behaviors is 

unclear. Some studies indicate that such 

behavioral changes are very temporary, 

whereas others imply that fish might not 

resume pre-seismic behaviors or 

distributions for a number of days. 

There appears to be a great deal of interand intra-specific variability. In the case 

of finfish, three general types of 

behavioral responses have been 

identified: startle, alarm, and avoidance. 

The type of behavioral reaction appears 

to depend on many factors, including 

the type of behavior being exhibited 

before exposure, and proximity and 

energy level of sound source. 

During the proposed study, only a 

small fraction of the available habitat 

would be ensonified at any given time, 

and fish species would return to their 

pre-disturbance behavior once the 

seismic activity ceased. The proposed 

seismic program is predicted to have 

negligible to low behavioral effects on 

the various life stages of the fish and 

invertebrates during its short duration 

(approximately 49 hours at each of 5 

sites on the Ninety East Ridge) and 

2700–km extent. 

Changes in behavior in fish near the 

airguns might have short-term impacts 

on the ability of cetaceans to feed near 

the survey area. However, only a small 

fraction of the available habitat would 

be ensonified at any given time, and fish 

species would return to their predisturbance behavior once the seismic 

activity ceased. Thus, the proposed 

survey would have little impact on the 

abilities of marine mammals to feed in 

the area where seismic work is planned. 

Some of the fish that do not avoid the 

approaching airguns (probably a small 

number) may be subject to auditory or 

other injuries. 

Zooplankters that are very close to the 

source may react to the shock wave. 

These animals have an exoskeleton and 

no air sacs. Little or no mortality is 

expected. Many crustaceans can make 

sounds and some crustaceans and other 

invertebrates have some type of sound 

receptor. However, the reactions of 

zooplankters to sound are not known. 

Some mysticetes feed on concentrations 

of zooplankton. A reaction by 

zooplankton to a seismic impulse would 

only be relevant to whales if it caused 

a concentration of zooplankton to 

scatter. Pressure changes of sufficient 

magnitude to cause this type of reaction 

would probably occur only very close to 


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Federal Register / Vol. 72, No. 68 / Tuesday, April 10, 2007 / Notices 17863 

the source. Impacts on zooplankton 

behavior are predicted to be negligible, 

and this would translate into negligible 

impacts on feeding mysticetes. 

Because of the reasons noted above 

and the nature of the proposed activities 

(small airguns and limited duration), the 

proposed operations are not expected to 

have any habitat-related effects that 

could cause significant or long-term 

consequences for individual marine 

mammals or their populations or stocks. 

Monitoring 

Either dedicated marine mammal 

observers (MMOs) or other vessel-based 

personnel will watch for marine 

mammals near the seismic source vessel 

during all daytime and nighttime airgun 

operations. GI airgun operations will be 

suspended when marine mammals are 

observed within, or about to enter, 

designated safety radii where there is a 

possibility of significant effects on 

hearing or other physical effects. At 

least one dedicated vessel-based MMO 

will watch for marine mammals near the 

seismic vessel during daylight periods 

when shooting is being conducted, and 

two MMOs will watch for marine 

mammals for at least 30 min prior to 

start-up of airgun operations. 

Observations of marine mammals will 

also be made and recorded during any 

daytime periods without airgun 

operations. At night, the forwardlooking bridge watch of the ship’s crew 

will look for marine mammals that the 

vessel is approaching, and execute 

avoidance maneuvers; the 180dB/190dB 

safety radii around the airguns will be 

continuously monitored by an aftlooking member of the scientific party, 

who will call for shutdown of the guns 

if mammals are observed within the 

safety radii. Nighttime observers will be 

aided by (aft-directed) ship’s lights and 

night vision devices (NVDs). 

Observers will be appointed by SIO 

with NMFS concurrence. Two observers 

will be on the vessel, and both will have 

gone through NOAA/NMFS training for 

marine mammal observations. Observers 

will be on duty in shifts usually of 

duration no longer than two hours. Use 

of two simultaneous observers prior to 

start up will increase the detectability of 

marine mammals present near the 

source vessel, and will allow 

simultaneous forward and rearward 

observations. Bridge personnel 

additional to the dedicated marine 

mammal observers will also assist in 

detecting marine mammals and 

implementing mitigation requirements, 

and before the start of the seismic 

survey will be given instruction in how 

to do so. 

The Roger Revelle is a suitable 

platform for marine mammal 

observations, and has been used for that 

purpose during the routine CalCOFI 

(California Cooperative Oceanic 

Fisheries Investigations). Observing 

stations will be at the 02 level, with 

observers’ eyes approximately 10.4 m 

(34 ft) above the waterline: one forward 

on the 02 deck commanding a forwardcentered, approximately 240° view, and 

one atop the aft hangar, with an aftcentered view that includes the 60–m 

radius area around the airguns. The eyes 

of the bridge watch will be at a height 

of approximately 15 m (49 ft); marine 

mammal observers will repair to the 

enclosed bridge and adjoining aft 

steering station during any inclement 

weather (unlikely at this place and 

season), and as necessary to use the 50 

X ‘‘big-eye’’ binoculars that are mounted 

there. 

Standard equipment for marine 

mammal observers will be 7 X 50 reticle 

binoculars and optical range finders. At 

night, night vision equipment will be 

available. The observers will be in 

wireless communication with ship’s 

officers on the bridge and scientists in 

the vessel’s operations laboratory, so 

they can advise promptly of the need for 

avoidance maneuvers or airgun powerdown or shut-down. 

The vessel-based monitoring will 

provide data required to estimate the 

numbers of marine mammals exposed to 

various received sound levels, to 

document any apparent disturbance 

reactions, and thus to estimate the 

numbers of mammals potentially 

‘‘taken’’ by harassment. It will also 

provide the information needed in order 

to shut down the GI airguns at times 

when mammals are present in or near 

the safety zone. When a mammal 

sighting is made, the following 

information about the sighting will be 

recorded: 

(1) Species, group size, age/size/sex 

categories (if determinable), behavior 

when first sighted and after initial 

sighting, heading (if consistent), bearing 

and distance from seismic vessel, 

sighting cue, apparent reaction to 

seismic vessel (e.g., none, avoidance, 

approach, paralleling, etc.), and 

behavioral pace. 

(2) Time, location, heading, speed, 

activity of the vessel (shooting or not), 

sea state, visibility, cloud cover, and sun 

glare. 

The data listed under (2) will also be 

recorded at the start and end of each 

observation watch and during a watch, 

whenever there is a change in one or 

more of the variables. 

All mammal observations and airgun 

shutdowns will be recorded in a 

standardized format. Data will be 

entered into a custom database using a 

notebook computer when observers are 

off duty. The accuracy of the data entry 

will be verified by computerized data 

validity checks as the data are entered, 

and by subsequent manual checking of 

the database. Those procedures will 

allow initial summaries of data to be 

prepared during and shortly after the 

field program, and will facilitate transfer 

of the data to statistical, graphical, or 

other programs for further processing 

and archiving. 

Results from the vessel-based 

observations will provide: 

• The basis for real-time mitigation 

(airgun shut down). 

• Information needed to estimate the 

number of marine mammals potentially 

taken by harassment, which must be 

reported to NMFS. 

• Data on the occurrence, 

distribution, and activities of marine 

mammals in the area where the seismic 

study is conducted. 

• Information to compare the distance 

and distribution of marine mammals 

relative to the source vessel at times 

with and without seismic activity. 

• Data on the behavior and movement 

patterns of marine mammals seen at 

times with and without seismic activity. 

Mitigation 

For the proposed seismic surveys in 

the Northeastern Indian Ocean during 

May August 2007, SIO will deploy two 

GI airguns as an energy source, with a 

total discharge volume of 90 in3. The 

energy from the airguns will be directed 

mostly downward. The small size of the 

airguns to be used during the proposed 

study will reduce the potential for 

effects relative to those that might occur 

with a large airgun arrays. 

In addition to marine mammal 

monitoring, the following mitigation 

measures will be adopted during the 

proposed seismic program, provided 

that doing so will not compromise 

operational safety requirements. 

Although power-down procedures are 

often standard operating practice for 

seismic surveys, it will not be used here 

because powering down from two guns 

to one gun would make only a small 

difference in the 180- or 190–dB radius 

– probably not enough to allow 

continued one-gun operations if a 

mammal came within the safety radius 

for two guns. Mitigation measures that 

will be adopted are: 

(1) Speed or course alteration; 

(2) Ramp-up and shut-down 

procedures; and 

(3) Night operations; 

Speed or Course Alteration – If a 

marine mammal is detected outside the 


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17864 Federal Register / Vol. 72, No. 68 / Tuesday, April 10, 2007 / Notices 

safety radius and, based on its position 

and the relative motion, is likely to 

enter the safety radius, the vessel’s 

speed and/or direct course may, when 

practical and safe, be changed in a 

manner that also minimizes the effect to 

the planned science objectives. The 

marine mammal activities and 

movements relative to the seismic vessel 

will be closely monitored to ensure that 

the animal does not approach within the 

safety radius. If the animal appears 

likely to enter the safety radius, further 

mitigative actions will be taken, i.e. 

either further course alterations or shut 

down of the airguns. 

Shut-down Procedures - If a marine 

mammal is detected outside the safety 

radius but is likely to enter the safety 

radius, and if the vessel’s course and/or 

speed cannot be changed to avoid 

having the animal enter the safety 

radius, the airguns will be shut down 

before the animal is within the safety 

radius (10 m (33 ft) for pinnipeds (190–

dB isopleth) or 40 m (131 ft) for 

cetaceans (180–dB isopleth)). Likewise, 

if a marine mammal is already within 

the safety radius when first detected, the 

airguns will be shut down immediately. 

Airgun activity will not resume until 

the animal has cleared the safety radius. 

The animal will be considered to have 

cleared the safety radius if it is visually 

observed to have left the safety radius, 

or if it has not been seen within the 

radius for 15 min (small odontocetes 

and pinnipeds) or 30 min (mysticetes 

and large odontocetes, including sperm, 

pygmy sperm, dwarf sperm, beaked, and 

bottlenose whales). 

Ramp-up Procedures – A ‘‘ramp-up’’

procedure will be followed when the 

airguns begin operating after a period 

without airgun operations. The two GI 

guns will be added in sequence 5 

minutes apart. During ramp-up 

procedures, the safety radius for the two 

GI guns will be maintained. 

Night Operations – At night, vessel 

lights and/or night vision devices 

(NVDs) could be useful in sighting some 

marine mammals at the surface within 

a short distance from the ship (within 

the safety radii for the two GI guns in 

deep water). Start up of the airguns will 

only occur in situations when the entire 

safety radius is visible with vessel lights 

and NVDs. 

Reporting 

A report will be submitted to NMFS 

within 90 days after the end of the 

cruise. The end of the northeastern 

Indian Ocean cruise is predicted to 

occur between July 16 and August 13, 

2007. The report will describe the 

operations that were conducted and the 

marine mammals that were detected 

near the operations. The report will be 

submitted to NMFS, providing full 

documentation of methods, results, and 

interpretation pertaining to all 

monitoring. The 90–day report will 

summarize the dates and locations of 

seismic operations, marine mammal 

sightings (dates, times, locations, 

activities, associated seismic survey 

activities), and estimates of the amount 

and nature of potential ‘‘take’’ of marine 

mammals by harassment or in other 

ways. 

Endangered Species Act 

Under section 7 of the Endangered 

Species Act (ESA) the NSF has begun 

consultation on this proposed seismic 

survey. NMFS will also consult on the 

issuance of an IHA under section 

101(a)(5)(D) of the MMPA for this 

activity. Consultation will be concluded 

prior to a determination on the issuance 

of the IHA. 

National Environmental Policy Act 

(NEPA) 

NSF prepared an Environmental 

Assessment of a Planned Low-Energy 

Marine Seismic Survey by the Scripps 

Institution of Oceanography in the 

Northeast Indian Ocean, May July 2007. 

NMFS will either adopt NSF’s EA or 

conduct a separate NEPA analysis, as 

necessary, prior to making a 

determination on the issuance of the 

IHA. 

Preliminary Determinations 

NMFS has preliminarily determined 

that the impact of conducting the 

seismic survey in the northeast Indian 

Ocean may result, at worst, in a 

temporary modification in behavior 

(Level B Harassment) of small numbers 

of 29 species of cetaceans. Further, this 

activity is expected to result in a 

negligible impact on the affected species 

or stocks. The provision requiring that 

the activity not have an unmitigable 

adverse impact on the availability of the 

affected species or stock for subsistence 

uses does not apply for this proposed 

action. 

For reasons stated peviously in this 

document, this determination is 

supported by: (1) the likelihood that, 

given sufficient notice through 

relatively slow ship speed and rampup, 

marine mammals are expected to move 

away from a noise source that is 

annoying prior to its becoming 

potentially injurious; (2) the fact that 

marine mammals would have to be 

closer than 40 m from the vessel to be 

exposed to levels of sound (180 dB) 

believed to have even a minimal chance 

of causing TTS; and (3) the likelihood 

that marine mammal detection ability 

by trained observers is high at that short 

distance from the vessel. As a result, no 

take by injury or death is anticipated 

and the potential for temporary or 

permanent hearing impairment is very 

low and will be avoided through the 

incorporation of the proposed 

mitigation measures. 

While the number of potential 

incidental harassment takes will depend 

on the distribution and abundance of 

marine mammals in the vicinity of the 

survey activity, the number of potential 

harassment takings is estimated to be 

small, less than a few percent of any of 

the estimated population sizes, and has 

been mitigated to the lowest level 

practicable through incorporation of the 

measures mentioned previously in this 

document. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to SIO for conducting a lowenergy seismic survey in the Indian 

Ocean from May - August, 2007, 

provided the previously mentioned 

mitigation, monitoring, and reporting 

requirements are incorporated. 

Dated: April 4, 2007. 

David Cottingham, 

Acting Deputy Director, Office of Protected 

Resources, National Marine Fisheries Service. 

[FR Doc. E7–6750 Filed 4–9–07; 8:45 am] 

BILLING CODE 3510–22–S 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[I.D. 010207B] 

Small Takes of Marine Mammals 

Incidental to Specified Activities; 

Seismic Surveys in the Beaufort and 

Chukchi Seas off Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice of receipt of application 

and proposed incidental take 

authorization; request for comments. 

SUMMARY: NMFS has received an 

application from Shell Offshore, Inc. 

(SOI) for an Incidental Harassment 

Authorization (IHA) to take small 

numbers of marine mammals, by 

harassment, incidental to conducting 

open-water offshore exploratory drilling 

on Outer Continental Shelf (OCS) oil 

lease blocks in the Beaufort Sea off 

Alaska. Under the Marine Mammal 

Protection Act (MMPA), NMFS is 

requesting comments on its proposal to 


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